There are four general types of checkpoints you might encounter: DUI checkpoints, U.S. border checkpoints, drug checkpoints, and TSA checkpoints. In a legal sense, they are not all created equal. So depending on which one you encounter, you’ll want to be prepared to flex your rights appropriately.

DUI Checkpoints

Sobriety checkpoints – also known as DUI checkpoints – are the most common roadblocks you might encounter. They function as a general-purpose investigatory tactic where police can get a close look at passing motorists by detaining them briefly. A roadblock stop is quick, but it gives police a chance to check tags and licenses, while also giving officers a quick whiff of the driver’s breath and a chance to peer into the vehicle for a moment.

Remember that your constitutional rights still apply in a roadblock situation. Though police are permitted to stop you briefly, they may not search you or your car unless they have probable cause that you’re under the influence or you agree to the search. As such, you are not required to answer their questions or admit to breaking the law.

Since the Supreme Court’s ruling in Illinois v. Caballes, police have more leeway to use drug-sniffing dogs in roadblock situations. There’s no need to waive your rights simply because dogs are present. But be advised that your legal options are limited if you’re arrested as a result of a dog sniff during a roadblock.

Also, keep in mind that police closely monitor cars approaching the roadblock. So you’re not likely to have any success trying to evade it.

The courts generally permit sobriety checkpoints, but only if conducted properly. If the police arrest you at a roadblock, always consult an attorney before confessing or agreeing to a plea bargain. There might be some legal options that your lawyer can pursue.

U.S. Border Checkpoints

Be aware that Customs and Border Protection (CBP) agents – which are part of the Dept. of Homeland Security (DHS) – are permitted to search you and your belongings at the U.S. border without probable cause or a search warrant. So anytime you cross the border, you consent to a search.

CBP may generally stop and search the property of anyone entering or exiting the U.S. If agents have reasonable suspicion to believe you’re concealing contraband, they may search your body using pat-down, strip, body cavity, or involuntary x-ray searches.

Searches of Electronic Devices

The Ninth Circuit Court of Appeals recently ruled that Homeland Security border agents must have reasonable suspicion before they can legally conduct a forensics search of laptops, mobile phones, camera memory cards, and other electronic devices.

Unfortunately, this limited ruling still permits agents to conduct a “quick look” laptop search, such as asking you to turn on your laptop to peek at open windows. So always password protect your files before crossing the border. And, of course, never voluntarily give agents your password.

Checkpoints Near the Border

Be aware that DHS agents have recently set up constitutionally-questionable “security checkpoints” up to 100 miles inside U.S. territory. If you should drive into one of these roadblocks, you are not required to answer the agent’s questions (usually starting with “Are you a United States citizen?”). Nor are you required to consent to any searches.

Check out the video below to see how DHS agents try to trick an intimidate people into compliance. Also, take note of the practical necessity of flexing your rights repeatedly.

Drug Checkpoints (it’s a trap!)

The Supreme Court has ruled that random checkpoints to find illegal drugs are unconstitutional. However, some police departments have devised a deceptive method to work around and exploit this restriction. Here’s how their trick works.

Police departments sometimes put up signs warning drivers of upcoming drug checkpoints. (This alone is not illegal.) But they will not pull over people who go through a checkpoint – because there technically is no checkpoint. Instead, officers will watch for vehicles approaching the nonexistent checkpoint and pull over vehicles who make illegal u-turns or discard contraband to avoid the fictitious “Drug Checkpoint Ahead.”

So if you see such signs, keep driving and don’t panic. If there’s a rest area following the sign, DO NOT pull into it. If you do, you might find yourself surrounded by drug-sniffing dogs.

Police departments, especially in the Mid-west, have been pushing their luck with this tactic, so if you encounter anything resembling an actual drug checkpoint, please contact that state’s ACLU Chapter. Similarly, if you’re arrested as a result of a real or fake “drug checkpoint,” you must contact an attorney to explore your legal options.

TSA Checkpoints

Be aware that Transportation Security Agency (TSA) agents –which are part of the Dept. of Homeland Security (DHS) – are permitted to search you and your belongings without probable cause or a search warrant anytime you pass through a TSA airport security zone.

The ACLU also keeps a Know Your Rights When Traveling page. It’s got handy tips for dealing with “spot interviews” and opting out of nude body scanners.

TSA’s Mysterious ID Requirement

Many folks are concerned about the TSA’s requirement that passengers show photo identification before passing through security. Of particular concern is TSA’s persistent refusal to release the text of the law that it uses to justify that requirement. For more on the sheer absurdity of the policy, read security expert Bruce Schneier’s insightful analysis.