The cow is dead on the side of the road. She is hollowed and blistered, her brown-and-white hide dried and leathery from the days, maybe weeks, in the unforgiving desert sun.

“That’s what migrants look like when we find them out here,” Mike Wilson says.

Sixty miles south of Tucson, cradled on the east by the Baboquivari Mountains, is the Tohono O’odham Nation. Once a seamless society spread across the sprawling Sonoran Desert, the Tohono O’odham (meaning “Desert People”) were split into two nationalities in 1853, when the U.S. purchased from Mexico the 29,640-square-mile region that is now southern Arizona and southwestern New Mexico. For nearly two centuries, the 75-mile border was seen as little more than a symbol by the O’odham people, who often travel between the United States and Mexico for doctor’s appointments, family gatherings, and religious events.

Even today, the Connecticut-sized reservation does not boast the towering steel fences seen in more populated border cities like Nogales and El Paso. Instead, the biggest barrier between the nations is a vehicle blockade, with a gate big enough for one car or truck to pass through at a time. This lack of physical border security—and plenty of impoverished residents willing to act as lookouts or drivers for money—has made the Nation a popular corridor for drug and human smuggling. Instead of erecting a wall, the reservation is swarming with Border Patrol agents, their green-and-white trucks often the only vehicles seen for miles.

Before 9 a.m. the sun is already searing through the cloudless cerulean sky and into our car. The dashboard thermometer climbs above 90 degrees. The air conditioner rattles on full blast. The main road that runs through the Tohono O’odham Nation is lined with Saguaros—the 25-foot, century-old cacti that tower over the desert with arms outstretched like an unofficial welcoming committee. But we are far from the Saguaros now, mere miles from Mexico, in an almost barren, sandy brown wasteland that looks like it might extend to the end of the earth.

Mike Wilson chuckles in the passenger seat as the car crawls in and out of cement craters at 5 mph on a road that looks like it’s been hit by a meteor shower. David Garcia is attempting to make a phone call in the backseat. The two middle-aged men, with silver ponytails hanging down their backs, are both members of the Tohono O’odham tribe. Yet they are, as Garcia says, “persona non grata on our own tribal land.”

Garcia is quiet. He speaks slowly, choosing his words carefully. He’s wary of reporters. He has tattoos on his fingers and forearms and is missing most of his teeth. If Wilson is the cheerful face of this operation, Garcia is the secret weapon, his years on the tribal council earning access to members of a typically closed-off culture.

Wilson, an ex-Presbyterian minister who says he was kicked out by his own congregants for leaving water for migrants, and Garcia, a former tribal council member, are on a mission to expose human rights violations by the U.S. Border Patrol on the Nation. They’ve been working with the ACLU—which has deemed the Tohono O’odham Nation “ground zero” for Border Patrol abuses against U.S. citizens—driving around the reservation, trying to rally enough tribal members to share their horror stories to build a class-action lawsuit. Wilson and Garcia say most tribal members have had altercations with Border Patrol agents. But on the Nation, these are the kinds of stories only whispered behind closed doors. So the two men have become pseudo-renegade detectives, following leads and asking the kinds of questions that, they say, have earned them the ire of the tribal people and government.

It was one of Garcia’s connections that brought him and Wilson to a tribal member who had been shot by a Border Patrol agent on the Nation in March.

When the duo arrived at Amon Chavez’s house they were greeted by a pit bull. They stayed in the car as the young man spoke to them from his driveway. He told them he’d been driving around with his cousin and a friend at the time of the shooting. He and his cousin, who was also shot, were taken to the hospital and when Amon woke up, the door to his room was guarded by a Border Patrol agent. When he was released from the hospital his cousin, the driver, was arrested.

According to an FBI press release, the only news report on the incident, one night in March an on-duty Border Patrol agent “opened fire...after a U.S. citizen tried to ram him with a truck.”

Two tribal members were shot and hospitalized and the agent who shot them was put on administrative leave. The Tohono O’odham Police Department was investigating the incident along with the FBI, who would likely pursue charges against Amon’s cousin, the driver, for assault on a federal officer. Any more information about who these men were, why the Border Patrol agent decided to open fire on them, and why the person who got shot would likely be hit with federal assault charges while the shooter received paid administrative leave, was nonexistent.

I’d soon learn that the mystery of the shooting of Amon Chavez and his cousin was emblematic of the struggle between the Border Patrol and the Tohono O’odham people. While many on the Nation view the Border Patrol as an occupying army, there is an unspoken, inherent fear of criticizing such a powerful agency of the federal government.

“It’s this whole culture of violence on the southwest border,” Wilson says. “The Border Patrol acts with impunity and immunity.”

***

This spring, an unprecedented number of unaccompanied minors crossed over the Rio Grande into Texas, flooding detention centers and, conveniently, monopolizing media attention. But before the “border crisis” dominated headlines, the issue of Border Patrol abuses was just coming to a boil.

In early May, The New York Times published the findings of a public records request by the D.C.-based American Immigration Council. Of the 809 complaints submitted to Customs and Border Protection’s (CBP) internal affairs office regarding abuses by agents within 100 miles of the U.S.-Mexico border between 2009 and 2012, only 13 resulted in disciplinary action. The reported incidents ranged from punching, kicking, and stomping on handcuffed detainees, to sexual abuse and inappropriate touching during searches. One pregnant woman reported that she suffered a miscarriage after she was kicked by a Border Patrol agent. Like so many others, she was left without recourse—she filed a complaint but the agent she accused of kicking her was not reprimanded, nor did she receive any notification that her complaint had been investigated. In the 13 cases that did result in disciplinary action for agents, this most often meant counseling.

Soon after, Border Patrol made public a very critical—and highly anticipated—government-commissioned report on the agency’s use of force policies. It was a review of the 67 cases of agents using deadly force, 19 of which resulted in death. The study, conducted by the nonprofit law enforcement advisory group Police Executive Research Forum (PERF), was actually published in November of last year, but the Border Patrol refused to release the report, drawing fire from the humanitarian and immigrants-rights activists. The agency also initially rejected PERF’s recommended policy changes, such as ending the practice of using deadly force against rock throwers or potential attackers in cars.

“We shouldn’t have carve-outs in our policy and say, except for this, except for that,” Border Patrol Chief Mike Fisher told the Associated Press in November, explaining why the agency would uphold its policy of allowing agents to use deadly force in any case where they felt their lives were in danger.

When the PERF report was finally released, alongside it was a brand new use-of-force policy handbook (PDF). One section of the report, in particular, examines 15 cases in which CBP agents fired shots at or into vehicles, cases like the mysterious March shooting on the Tohono O’odham Nation.

“It appears that CBP practices allow shooting at the driver of any suspect vehicle that comes in the direction of the agents,” despite the fact that “a half ounce (200 grain) bullet is unlikely to stop a 4,000 pound moving vehicle, and if the driver of the approaching vehicle is disabled by a bullet, the vehicle will become a totally unguided threat,” the PERF report’s authors observed.

While the Border Patrol is technically a law enforcement agency, much of the language used by field agents is borrowed from the military, making daily operations sound more like combat than police work. For example, agents along the southwest border pursue UDAs (undocumented aliens) using a version of the military “defense in depth” strategy—catching migrants once they’ve already crossed the border rather than preventing them from getting in. Even the way the term “aliens” is used to describe migrants spotted in the desert has an air of hostility.

President Obama often touts the Border Patrol’s vast expansion—though set in motion by his predecessor—as proof of his dedication to border enforcement. In the wake of 9/11, Border Patrol and its umbrella agency, CBP, became a part of the newly minted Department of Homeland Security. Between 2004 and 2011, the U.S. Border Patrol force doubled in size to nearly 21,000 agents. That doesn’t even include the 21,650 customs officers stationed at U.S. ports of entry, making the CBP the country’s largest law enforcement agency. But critics argue that the rushed background checks and lowered hiring standards that were required for such growth are to blame for numerous reports of corruption, unnecessary use of deadly force, and abuses of power by agents.

According to one study (PDF) published last year by the Government Accountability Office, 150 CBP employees were convicted of or charged with corruption between 2004 and 2011. Agents averaged nearly nine years on the job before getting caught for accepting bribes or allowing illegal drugs to cross the border. From 2004 to 2012, there were 2,170 reported employee arrests. Polygraph tests did not become mandatory for Border Patrol and CBP applicants until October of 2012 and, in the first six months after the program was implemented, more than 200 applicants confessed to a host of heinous crimes including rape, murder, child molestation, drug and human smuggling, bestiality, and plotting to assassinate President Obama. Internal records of these polygraph admissions obtained by the Center for Investigative Reporting raised serious concerns about the thousands of people who were hired before polygraphs were required.

“This is the largest federal law enforcement agency in the country operating as if it were a few hundred guys on horseback and not 21,000 Border Patrol agents with billions of dollars at their disposal,” says James Lyall, an attorney with the ACLU’s Border Litigation Project in Tucson, a year-old project that investigates and prosecutes cases of human-rights abuses on the southwest border. He says it’s particularly difficult to document cases on the Tohono O’odham Nation. That’s why he’s enlisted Mike Wilson and David Garcia to engage tribal members who wouldn’t normally be willing to come forward.

“It’s about the institution, it’s not about individual officers,” says Juanita Molina, executive director of two Tucson-based humanitarian groups, Border Action Network and Humane Borders. Around here, she’s known as the person to talk to about border issues. But like everyone else, even Molina is in the dark about why two unarmed tribal members were shot by an agent on the Nation in March.

“Who knows what happened with those guys, but doesn’t it show a certain kind of over-response that they got shot?” she says.

“The reality is the entire U.S.-Mexico border is militarized and that presence in everyday life is incredibly oppressive,” Molina says. “You have a lot of agents here who are coming back from the war and they’re already in an agitated state. Then you stick them out in the darkness of the high desert and we see these extreme reactions, using a level of force that doesn’t make sense.”

***

The Border Patrol “mission” has remained, from Prohibition to Homeland Security, to keep unauthorized foreign goods from entering the country. The definition of these goods has changed over the years. When the Border Patrol was first established in 1924, it was alcohol. Since 2004, when the agency became a part of the post-9/11 Department of Homeland Security, it’s been, technically, terrorists and weapons of mass destruction.

“I know it sounds kind of crazy because you think, ‘What does the Mexican border and the Canadian border have to do with terrorism?’” Agent Peter Bidegain says. “But Border Patrol apprehends people from literally all over the world. Last year we apprehended people from literally almost every country in the world.”

Bidegain looks and sounds like he was born to wear the green Border Patrol uniform. It’s crisp and perfectly pressed, even in the 100-degree sauna that is Tucson in June. Black plastic sunglasses rest atop his buzzed hair, above a tanned face with sharp features. His voice is deep and affirmative, like an All-American football player’s. Except when he speaks Spanish. That accent he learned from his Basque grandfather.

One of the few Arizona natives on a force comprised largely of Midwesterners unfamiliar with desert terrain, Bidegain worked in marketing for seven years before joining the force in 2010. After three years in the field, most of them spent working nights in Nogales, he became a public information officer last July.

Bidegain has never been assigned to work on the Tohono O’odham Nation but he is familiar with the triangular tension that exists between the tribal government, the people, and the Border Patrol. He notes that agents who are assigned to patrol the Nation are required to attend a cultural sensitivity training, organized by tribal leaders to familiarize themselves with sacred sites and rituals of the O’odham people. The tribal government, which is represented by a local public relations firm, did not respond to a request for comment on this story.

The dashboard radio crackles with reports of migrant sightings as Bidegain drives his white-and-green Border Patrol truck down I-19 South towards Nogales. At the checkpoint, cars and trucks line up to pass through a white, tented archway extending across the northbound side of the highway. A CBP dog sniffs around for contraband like drugs, food, weapons, people. An agent asks each driver if they are a U.S. citizen, and watches for signs of nervousness, like a protruding neck vein or quivering voice. Suspicious vehicles are pulled over for secondary inspection, and drivers and passengers are questioned inside an air-conditioned trailer not wide enough for two people to stand side by side comfortably. Beyond a few large computer screens, chairs, a first aid kit, and a stack of water bottles is a small, metal holding cell. I step inside and touch the door and the back wall of the cell with ease. This is where people can be held, sometimes for hours, while agents ask questions, run background checks, and search cars.

Checkpoints like this one and the 33 others along the southwest border are the source of frustration for the towns they occupy. Having to declare one’s citizenship to drive to a different town—which, in some remote places, can mean a trip as simple as the grocery store—is enough to make a person feel like a trespasser in their own neighborhood. But beyond the inconvenience, it’s unclear what rights citizens have at these checkpoints, or when pulled over by a roving Border Patrol agent.

Bidegain insists the media have perpetuated a misperception that the Border Patrol operates under its own set of rules. Agents need to develop a certain level of reasonable suspicion to pull someone over, or to search their car, he tells me. But “reasonable suspicion” is not the same thing as probable cause. Merely driving near the border can be enough to raise an agent’s suspicions. So can refusing to have your car searched. Or looking foreign.

“People should certainly ask why this is happening, or say they’d rather not have their car searched,” Bidegain says. “But if you feel like your rights are being violated, the time and place for that isn’t necessarily on the ground while the incident with the agent is taking place. You’re only going to escalate it.” Instead, he says, file a complaint.

It’s a good idea in theory. But given the agency’s lack of transparency and its reluctance to follow through on investigating complaints of abuses, it’s an argument that sounds designed to discourage people from speaking up.

Shouldn’t a border resident have as much right as anyone else to drive somewhere without being treated like a suspected criminal?

Bidegain pauses.

“Absolutely,” he says. “As a person who lives in the U.S., I absolutely understand that.”

When I ask Bidegain about the shooting of Amon Chavez, he tells me he’s heard about it. He doesn’t know any details. I ask who would be the right person within the Border Patrol to talk to about it. He says it would be him.

***

“This is our nation’s capital,” David Garcia says with a sarcastic laugh as we pull into Sells, the capital of the Tohono O’odham Nation. In 2000, 46 percent of the 2,799 residents here lived below the poverty line. Three stray dogs saunter out of our way as we turn into a residential area lined with trailers and graffiti-sprayed stop signs.

Trailers are the most common type of dwelling for tribal members who do not qualify to live in a house built by the U.S. Department of Housing and Urban Development, or HUD. Wilson, who grew up off the reservation in a tiny former copper mining hub called Ajo, says programs like HUD housing eliminate the incentive for tribal people to buy their own homes. Rooted in this dependency on the federal government, he says, is the reluctance across the Nation—but especially within the tribal government—to speak out against Border Patrol abuses.

“My fear is that the promise of HUD housing, the hope of HUD housing, in a way buys tribal silence,” Wilson says as he looks at the mobile homes. One is burned and damaged; another looks like a 1960s-style Airstream buried in a pile of old furniture, toys, and other junk. “It buys a lack of critical voice because the perception is, ‘I don’t want to criticize the Border Patrol because that may be perceived as criticizing the U.S. government.’”

Art Garcia, Gloria Zazueta, and their 12-year-old daughter, Amanda, greet us outside Art’s mother’s home. Inside a workshop-like porch attached to the main trailer, metallic wreaths made of brightly colored ribbon and synthetic flowers hang on the wall. Framed prints of ubiquitous oil paintings like Raphael’s cherubs sit on a rotating wire rack. We arrange ourselves in a circle on metal foldout chairs and a futon. A single electric fan provides some relief from the late afternoon heat.

Gloria opens a folder filled with legal documents, incident reports, and handwritten notes. Her eyes dart through oval, wire-rimmed glasses that rest gently on her round cheeks. Too many bad experiences with Border Patrol have taught her to save everything.

To Gloria’s left is Art. He is at least 6 feet tall, and broad, with deeply set almond-shaped eyes and the calloused hands of a man who has spent years riding horses and wrangling cattle. Usually a rancher of few words, when it comes to the Border Patrol, Art has a lot to say.

“The big problem is this is federal land, they are federal agents, and they can do whatever they want,” Art says, his mustachioed mouth barely moving when he speaks.

Art and Gloria don’t know the men who were involved in the shooting a few months ago, but they’ve heard about it. The premise, unfortunately, is all too familiar.

Art traps cattle for different ranches on the Nation, spending hours herding cows into designated areas and making sure they can’t get out. He works in remote areas at all hours of the day, drawing the attention of Border Patrol. One of his horses was smashed and killed by a speeding Border Patrol truck and he’s lost a number of cows thanks to agents cutting his fences while tracking footprints.

On his way home one night, Art was pepper-sprayed, thrown on the ground, and handcuffed when he told a pair of Border Patrol agents looking to search his truck that his steering wheel was broken and he’d rather not turn the engine off for fear it wouldn’t restart. Later, when Art asked for an explanation, he was told that the agents had caught a group of migrants earlier and “were just on an adrenaline rush.”

Once he was out chopping wood with eight other men when a gun-toting agent told him, “I can take you all out right here and now and there’s nothing anyone can do for you.” Art whistled for the other guys and when they came out of the woods carrying their axes, the agent yelled into his radio for backup. Two more rifle-wielding agents were there within minutes.

“I was just walking back and forth standing in front of the gun, I didn’t want anyone else to get shot,” Art says when I ask whether he thought the agent was actually going to shoot him. He managed to get Gloria on the phone, who called the nearby Border Patrol sector chief and the whole ordeal was over as soon as it had escalated.

Then Art and Gloria were pushed too far.

Art was parked on the side of Federal Route 19 one January afternoon in 2010, waiting to pick up his daughter from the school bus stop like he always did. He leaned his seat back, lit a cigarette, and waved to a Border Patrol agent driving by at about 5 mph. Because he had about 45 minutes to kill before Amanda’s bus arrived, and because he didn’t see anyone else around, Art decided to clean his rifle.

He stuck the barrel of the gun out his window and started wiping it down with a rag. He noticed a Border Patrol agent parked down the street at an angle in front of him, but after a few minutes he looked up again and the agent was gone. Two Border Patrol vehicles drove past him in opposite directions and parked near the woods behind him. Art started to drive off, but then, because he still had to pick up his daughter and since he wasn’t doing anything wrong, he made a U-turn and parked in the same spot. When he pulled up, one of the Border Patrol agents was parked facing his car head on with his weapon drawn.

Still in his car, Art called Gloria, then the Tohono O’odham Police Department. He got a busy signal from the cops, but Gloria pulled up next to him within minutes. When she arrived, Art was on the phone with the local Border Patrol substation, explaining that he now had two Border Patrol agents facing him at gunpoint. He was told on the phone to comply with the agents. But no one had even approached Art. He had no idea what was going on.

Then the school bus pulled up and Amanda got out. The agent who had been pointing his gun at Art walked over to the bus driver, his weapon in hand, and told the driver to reverse the bus. The driver refused and the agent yelled at Amanda to “get back on the fucking bus.”

Art says the agent asked him repeatedly if he had any other weapons, to which he replied that he had another rifle in the truck and a knife on his belt, holding his arm out to the side so the agent could see the blade. The agent then told him he was being arrested for assault on a federal agent. Art says he was swarmed by the five Border Patrol agents who pulled at his arms, pepper-sprayed him, and pushed him to the ground, one kneeling on his head as he read his Miranda Rights. Amanda and the 20 kids on the school bus watched with horror, many of them crying.

Despite complaining that he was asthmatic and was having trouble breathing, Art says he was put in the back of a Border Patrol vehicle and taken to a substation on the Nation where he was held for nearly five hours and then let go without a charge. Amanda can’t talk about that day without crying.

Art and Gloria filed a formal complaint to the Border Patrol, complete with letters from a child psychologist who evaluated Amanda after the incident and the parents of children who were also on the bus that day. They also hired an attorney and filed a federal tort claim against Customs and Border Protection for personal injury. The claim was dismissed because, as U.S. Border Patrol Deputy Chief Ronald Vitiello wrote in a letter to Art and Gloria’s lawyer, “the loss cannot be attributed to a wrongful or negligent act or omission on the part of a U.S. Customs and Border Protection employee.”

As for their complaint?

“They won’t ever tell you what action they take,” says Gloria. “They could have thrown it in the garbage for all we know.”

Art says the school bus incident really brought tribal members out of the woodwork, sharing with him their own negative experiences with the Border Patrol. Exhausted by the circular complaint process and failed attempts at legal action, though, Art says the only reason he’s had less trouble with Border Patrol lately is because he finally took a stand.

At a recent district meeting where Border Patrol agents and tribal leaders were present, Art says he raised his hand with a warning:

“I’ve been pulled over, pepper-sprayed, beat on. Now it’s gotten to where I’ve been assaulted at gunpoint. I’m in fear of my life. If any of your agents come running up to my vehicle I will defend myself because of the threats that I’ve had. I ain't gonna take it anymore. So you make sure your agents are aware that it's me, because I ain’t takin’ this anymore.”

***

“5 bullete holes, a fractured spine, one broken rib and some bruised lungs,” Amon Chavez wrote on April 3. “Man am I lucky.”

No one I spoke to in Arizona had any concrete details about the shooting on the Tohono O’odham Nation. In fact, it wasn’t until I’d left there that I finally found some answers—on Facebook.

Chavez had posted status updates about his recovery, alongside images of friends and the Insane Clown Posse. A month after I reached out to him, he told me what happened that night.

Chavez, his cousin Shawn Miguel, and his brother-in-law, Raymus Listo, were at Chavez’s house “drinking, laughing, and enjoying each other’s company” when they decided to go for a drive. Chavez admits they were drunk, “but DEFINITELY not out looking for trouble.” It was around midnight. With Miguel in the driver’s seat, they drove down the road from Chavez’s house, made a U-turn in the dirt road in front of a building, and headed back toward home. That’s when Chavez says they saw the headlights of a Border Patrol vehicle facing them head-on.

According to a complaint filed in federal court on behalf of the U.S. government, at approximately 12:15 a.m. on March 31, 2014, Border Patrol Agent Joseph Spann was parked at an intersection near the San Miguel village on the Tohono O’odham Nation. Spann said he was standing between the door and the driver’s seat of his marked vehicle when he noticed a maroon Dodge pickup truck slow down, turn in his direction, and then speed up. According to Spann’s account, he jumped into his vehicle, drew his weapon, and fired on the truck as it approached. The truck then struck the driver’s side of Spann’s vehicle and kept moving.

In Chavez’s version of the story, Miguel was driving steadily in the direction of Spann’s vehicle like he was going to wave hello to the agent, when he veered quickly to avoid a tree and some shrubs jutting out into the road. Not knowing how close he was, Chavez says, Miguel scraped the driver’s side door of the Border Patrol vehicle.

“POP!POP!POP!POP! The agent unloaded kill shots straight into our vehicle basically from window to window,” Chavez wrote to me. “I’m in the passenger seat crouching down, hearing these loud shots filling the inside of the cab, just exploding. My brother-in-law is ducked in the backseat and he yells out to my cousin, ‘Go, drive, he’s shooting us.’ So my cousin puts it in drive and we steadily drive away still being shot at.”

A short distance away from where the shooting took place, according to the complaint, Border Patrol and Tohono O’odham Police officers located the maroon truck and two men, Shawn Miguel and Amon Chavez. Both had been shot—Miguel in his face and shoulder and Chavez three times in his back and once in the arm—and were airlifted to the University Medical Center in Tucson. Farther away, police found Raymus Listo. When he first arrived at the hospital, Amon says his room in the ICU was guarded by Border Patrol agents until he was questioned by the FBI. He can’t say what they asked him.

Shawn Miguel was formally indicted on April 30 on one count of assault on a federal officer with a deadly weapon—a charge that carries a maximum sentence of 20 years in prison. According to court documents, his case is set for trial on October 21. Miguel initially told me via Facebook that he wanted to share his side of the story, but he later declined to comment while his case is pending. Miguel’s public defender did not return multiple requests for comment. The assistant U.S. attorney prosecuting his case declined to comment.

According to the brand new Border Patrol Use of Force Policy Handbook (PDF), agents “shall not discharge their firearms at the operator of a moving vehicle...unless deadly force is necessary” and the agent must have “a reasonable belief that the operator poses an imminent danger of serious physical injury or death to the agent or to another person.”

Maybe Agent Spann really did think the pickup truck was charging at him and that the only way to defend himself was to shoot. Or like Art Garcia, maybe Miguel, Chavez, and Listo just got caught up in the wrong agent’s adrenaline rush. Maybe we’ll never know.

Because when the sun sets behind the Baboquivari Mountains, the Tohono O’odham Nation goes dark. The streets are unlit; the drivers are blind to anything more than a few inches beyond their headlights. This is where the Border Patrol roam. It’s a place where an agent shoots two unarmed men and no one asks why. A place so vast, so quiet, so remote, so deep in the shadows of the United States, that anything can happen and it wouldn’t make a sound.

Editor's Note: "An earlier version of this story said that “The legal authority that U.S. Customs officials have to stop and search every person or vehicle that enters the U.S. without a warrant or probable cause is technically extended to Border Patrol agents within 100 miles of the border.” While CBP regulations make it sound like that is the case, Supreme Court and federal court rulings state that agents must have a warrant or probable cause to conduct a search outside a Port of Entry.