Immigrants are getting caught between federal and state marijuana laws.

US Citizenship and Immigration Services (USCIS), the federal agency in charge of processing visa and citizenship applications, has been rejecting immigrants who work for the marijuana industry or have admitted to using the drug in states where it’s legal, immigration lawyers and advocates say.

It’s yet another example of how the contradiction between state and federal laws is spilling over beyond issues related to the legal marijuana industry itself. While 33 US states and the District of Columbia allow some kind of pot use, the drug remains illegal when it comes to any kind of federal matter, including green cards and naturalization.

Friction between federal and local authorities has been increasing under the Trump administration, which is less tolerant than its predecessor when it comes to both immigrants and local pot laws.

Yesterday, USCIS issued a bulletin (pdf) underscoring that marijuana use is a disqualifying factor in citizenship applications, regardless of whether it’s legal locally.

Drug use is not a new USCIS criteria—the agency has long used it to determine whether an immigrant has “good moral character” and deserves to stay in the US. But until now, denials related to legal pot have been mostly seen in Colorado and Washington, the two states that first legalized recreational marijuana, says Kathy Brady of the Immigrant Legal Resource Center (ILRC), a California nonprofit that advocates for immigrants’ rights.

Brady fears the new policy bulletin will mean more marijuana-related denials as USCIS officers extend the practice to other states that have legalized the drug. She tells Quartz the announcement is “part of the Trump administration’s plan to get rid of or block as many immigrants as they can.”

A USCIS spokesperson says the bulletin is consistent with federal law, under which marijuana is considered a prohibited substance in the same category as LSD or ecstasy.

USCIS’s probing

There are several ways in which USCIS can find out if someone has used drugs. The most straightforward is by asking, either through an application or during an interview, whether an immigrant has abused drugs or broken the law.

For example, one green-card applicant who is married to an American citizen now risks being deported after an immigration officer asked him if he had ever used marijuana. The man replied that he had tried it once or twice at parties since DC legalized pot, but that he didn’t like it.

“Just by admitting that, he was declared permanently inadmissible,” says Brady, who was introduced to the man through his attorney. “He did not get a green card and now he could be deported.”

Drug use can also come up during the required health exam for green-card applicants. The doctor performing it can order a drug test for a variety of reasons, including a history of substance abuse, physical or psychological signs of a drug problem, or even long gaps between schooling or employment.

Marijuana industry jobs

A place of employment with a cannabis-related name is another red flag for USCIS. Even an accountant or a secretary working for someone in the marijuana industry could be considered to be trafficking in a controlled substance, in the federal government’s eyes.

Jeff Joseph, a Colorado-based immigration lawyer, says he gets at least a case a week involving someone who is no longer eligible to become a citizen because they’ve worked at a pot company. USCIS may even deny benefits to the immigrant spouses of, say, dispensary workers, because they’ve technically benefitted from the profits of selling drugs, he says.

“Marijuana has significant consequences across the board for all types of immigration applications,” he adds.

More awareness

The new USCIS guidelines will likely raise awareness of the pitfalls associated with legal pot use. Many people don’t even realize what they’re doing is illegal under federal law.

Joseph, for example, says he recommends that clients invoke their right against self-incrimination under the Fifth Amendment when USCIS asks them about marijuana.

The ILRC, meanwhile, advises non-citizens to never leave the house carrying marijuana or paraphernalia, a medical marijuana card, or wearing clothing with marijuana imagery on it. It also recommends that immigrants not have anything pot-related on their phones, or post messages on social media—which is reportedly monitored by immigration authorities—about any personal relationship with the drug.

It concludes: Only people who are already US citizens can use marijuana or work in the legal industry without any concern.