What are my rights if questioned by immigration enforcement on a US domestic flight?

Constitutional law professor Garrett Epps has covered this incident in an article for the Atlantic. He concludes that by law, an agent in this situation should allow passengers who refuse to comply to pass.

Based on his research, Epps concludes that officials lack the authority to perform mandatory check of every passenger:

After days of research, I can find no legal authority for ICE or CBP to require passengers to show identification on an entirely domestic fight. The ICE authorizing statute, 8 U.S.C. § 1357, provides that agents can conduct warrantless searches of “any person seeking admission to the United States”—if, that is, the officer has “reasonable cause to suspect” that the individual searched may be deportable. CBP’s statute, 19 U.S.C. § 1467, grants search authority “whenever a vessel from a foreign port or place or from a port or place in any Territory or possession of the United States arrives at a port or place in the United States.” CBP regulations, set out at 19 C.F.R. § 162.6, allow agents to search “persons, baggage, and merchandise arriving in the Customs territory of the United States from places outside thereof.”

Epps further writes that “I asked two experts whether I had missed some general exception to the Fourth Amendment for passengers on a domestic flight”, and quotes them in the piece agreeing that a mandatory check would not be legal, and that there is no exception for domestic aviation.

Epps also reached out to CPB, who are quoted claiming that the incident did not constitute a mandatory check, but a request for “consensual assistance”:

In this situation, CBP was assisting ICE in locating an individual possibly aboard the flight that was ordered removed from the United States pursuant to the Immigration and Nationality Act. To assist ICE, CBP requested consensual assistance from passengers aboard the flight to determine whether the removable individual in question was in fact aboard the flight. In the course of seeking this assistance, CBP did not compel any of these domestic passengers to show identification. With much-appreciated cooperation from these passengers, CBP was able to resolve the issue with minimal delay to the traveling public.

Epps notes that such requests for “voluntary cooperation” are perfectly legal, even if the officers involved block an exit, ask for documents, and do not tell anyone that they are not legally required to comply.

At the end of the article, Epps concludes that passengers should be able to pass without complying, but suggests that there a degree of risk in doing so:

I have researched the matter, and feel reasonably confident that an agent would have to let me pass if I refused the demand for my papers. If not, I can afford counsel and my family knows excellent lawyers to call.

Do I have the right to refuse compliance if asked for documentation?

You have a fifth-amendment right against incriminating yourself, so you can refuse to comply. However, depending on the legal authority for checking your ID, the officers can probably detain you until they’ve determined your immigration status, or whatever other facts are relevant to their investigation. Under certain circumstances, they can search your person and property, which will most likely give them access to your documents even without your consent.

If I refuse compliance or cannot produce documentation, can officials detain me at the airport, pull me off a plane that hasn’t yet departed, or prevent me from boarding a connecting flight?

Yes. If they have probable cause to suspect you of a crime, they can arrest you. If they have reasonable suspicion, they can detain you to investigate that suspicion. In some cases, reasonable suspicion is not required.

Are there possible long-term consequences if I refuse to comply? Are the consequences different if I am a US citizen, a foreign national with a valid visa or green card, or an alien in the country without proper documentation?

This is immigration enforcement, so of course the long-term consequences depend on your immigration status. If you can prove that are a US citizen, or that you are an alien in compliance with immigration law, there can be no long-term consequences related to immigration violations, so you only need to worry if you are charged with other crimes. For aliens who are present in violation of immigration law, the long-term consequences could be significant indeed, up to and including detention and deportation.