Protesters gathered outside Terminal 4 at John F. Kennedy International Airport on Saturday in opposition to President Donald Trump's proposed ban on immigration. REUTERS/Stephen Yang President Donald Trump signed an executive order last Friday halting refugee arrivals into the US for 120 days and barring citizens of Iraq, Iran, Sudan, Libya, Somalia, Syria, and Yemen from entering the US for 90 days.

Prior to the immigration ban, however, Trump signed another executive order, titled "Enhancing Public Safety in the Interior of the United States," containing a section that expands the role of immigration officials to admit, detain, or deport individuals.

While the immigration ban was met with an immediate backlash from both Republican and Democratic politicians, as well as thousands of demonstrators at the US's most trafficked airports, experts say the earlier executive order contains sections that could have a massive impact on the US's immigration policy.

The devil is in the details

Buried in the text of the earlier executive order is a section that could have widespread implications for the enforcement of immigration laws.

Take a look at Section 5:

"Sec. 5 Enforcement Priorities. In executing faithfully the immigration laws of the United States, the Secretary of Homeland Security (Secretary) shall prioritize for removal those aliens described by the Congress ... as well as removable aliens who: "(a) Have been convicted of any criminal offense; "(b) Have been charged with any criminal offense, where such charge has not been resolved; "(c) Have committed acts that constitute a chargeable criminal offense; "(d) Have engaged in fraud or willful misrepresentation in connection with any official matter or application before a governmental agency; "(e) Have abused any program related to receipt of public benefits; "(f) Are subject to a final order of removal, but who have not complied with their legal obligation to depart the United States; or "(g) In the judgment of an immigration officer, otherwise pose a risk to public safety or national security."

Immigration lawyers whom Business Insider spoke with had two major concerns regarding Section 5.

Protesters at JFK airport in New York on Saturday. Associated Press/Craig Ruttle

The first concern is that Section 5 seems to go beyond Trump’s suggestion during his campaign that, at least initially, he would prioritize only immigrants charged with crimes for deportation.

The broad list of criteria would apply to essentially every immigrant living in the US illegally, making them all an "enforcement priority," according to Mario Machado, a Florida-based criminal defense and immigration attorney who wrote about the order in "Fault Lines," part of the legal-news website Mimesis Law.

The section's repeated use of "any," Machado said, suggests that all convictions, no matter how minor, could become cause to "trigger an enforcement priority and the expenditure of government resources for detainment and deportation."

Machado went on to describe Section 5 as creating "a federal mandate to snare any and all convicts, no matter how small the peccadillo."

The Obama administration's previous rules, established in a 2014 memo, laid out two specific priorities for officials from two law-enforcement agencies tasked with handling immigration. It prioritized for deportation immigrants living in the US illegally who pose a "threat to national security" as well as those who have been convicted of repeat offenses or "significant misdemeanors" like sexual assault or burglary.

The two agencies, Immigration and Customs Enforcement, known as ICE, and US Customs and Border Protection, known as CBP, are housed within the Department of Homeland Security. CBP enforces immigration laws at the border, while ICE is responsible for enforcing immigration laws and carrying out deportations. Immigration advocates see both of those agencies' roles expanding under Trump.

Port Authority Police Department officers blocking protesters gathered outside Terminal 4 at JFK airport on Saturday. REUTERS/Stephen Yang

"Trump's new order is a go-get-'em-all approach," Stefanie Fisher, an immigration lawyer who is a partner at the Boston-based firm Araujo & Fisher, told Business Insider. "The goal now seems to be to arrest everyone."

Fisher's main concern, or what she called "the real danger," is that increasing the number of those subject to deportation could cause ICE and CBP officials to overlook people who pose genuine threats to national security. For example, a person who was charged with driving without a license could attract the attention of officials who would otherwise be focusing on identifying those engaged in terrorism or espionage.

Claude Arnold, a former ICE special agent who now works for Frontier Solutions, a Virginia-based crisis-management firm, told Business Insider that in his 27 years working as an ICE special agent, resource allocation was "never an issue."

"Line-level employees want to go after the big fish," Arnold added. "They have huge caseloads. They don't have time to just be going out and arresting someone just because they're an illegal alien."

Another factor that suggests immigration officers may not crack down on minor offenses is detention space: There's only so much room to hold people awaiting deportation, and Arnold said that if officers were continually bringing in low-level offenders, those offenders would "be kicked out of the backdoor."

A CBP officer. US Customs and Border Patrol

The second concern immigration advocates share is that Section 5, subsection (g), directs officials to prioritize removing "aliens" who in "the judgment of an immigration officer, otherwise pose a risk to public safety or national security."

Immigration advocates are concerned that the language leaves the decision of who is detained, admitted, or deported from the US up to the judgment of ICE and customs officials.

"It's a very vague, very opaque rule that's likely to be inconsistently applied," Reaz Jafri, an immigration lawyer who is a partner at Withers Bergman and spent Saturday at John F. Kennedy International Airport in New York working with those affected by Trump's temporary immigration ban, told Business Insider. "The decision to admit, or detain a person is in the unchecked hands of customs officers."

The National ICE Council, a union representing ICE officials, said in a statement that the Trump administration had "empowered" the agency's officials to "allow law enforcement to do its job."

"The men and women of ICE and Border Patrol will work tirelessly to keep criminals, terrorists, and public safety threats out of this country, which remains the number one target in the world — and President Trump's actions now empower us to fulfill this life saving mission, and it will indeed save thousands of lives and billions of dollars," the union said.

A woman greeting her mother after she arrived from Dubai on Emirates Flight 203 at John F. Kennedy International Airport in Queens, New York, on January 28. Andrew Kelly/Reuters

Jafri, however, took issue with the idea that customs officers, most of whom have no legal training, be allowed to make those decisions without oversight. Under the Obama administration, Jafri said, customs officers applied a law with much stricter precedents, guidelines, and regulations than those laid out in Trump's executive action.

"That all seems to have gone out the door," he said.

Arnold, meanwhile, believes that Trump's executive order simply restores the "long-standing" authority for discretion that he said ICE and CBP officers had before Obama's priority-enforcement guidelines. The Trump administration's executive order terminated the enforcement priorities laid out in Obama's 2014 memo.

"Law enforcement need all their authorities available to be productive," Arnold added. "All I see that this executive order has done is restore discretion to the line-level agent or officer, and leave it up to them to decide how to exercise their authority."

It remains to be seen how or whether Trump’s executive action will change the conduct of ICE and CBP officials. The sudden rollout of Trump's immigration ban was heavily criticized as being disorganized, with Jafri, for example, pointing to confusion over how to treat those who held dual citizenship in one of the countries affected by the ban.

Jafri said that even after the US announced exemptions for dual citizens with passports from unrestricted countries, he was still cautioning one of his clients, a dual Iranian-Canadian national who resides in the US, from leaving the country.

Moving forward, the steady trickle of executive orders from the Trump administration means that for immigration lawyers and border officials, confusion still reigns.

"Whatever I say now," Jafri said, "may not be applicable in 48 hours."