Under a new guidance issued by U.S. Citizenship and Immigration Services (USCIS), immigrants may find themselves barred from obtaining citizenship if they possess or use marijuana—even if doing so is legal where they live. The new policy also clarifies that even employment in the industry can prevent an immigrant from being a naturalized citizen.

As more states legalize medical and recreational marijuana, immigrants may find themselves entirely left out.

Under the federal Controlled Substances Act, marijuana remains a Schedule I controlled substance. Possession of even small amounts of marijuana can qualify as a federal misdemeanor. Giving marijuana to another person—even for no money—can qualify as trafficking.

To be eligible to become a naturalized citizen, an immigrant must demonstrate they had “good moral character” for the past five years before filing their application. But the law presumes that a person does not have “good moral character” if they have committed any violations of controlled substance laws. This is the case even if they were never arrested or convicted. There is an exception for those with a “single offense of simple possession of 30 grams or less of marijuana.”

Because the federal government hasn’t interfered with state legalization, many immigrants may have been unaware of these consequences. But USCIS has now made it clear that state laws do not prevent immigration consequences.

According to the guidelines, “possession of marijuana for recreational or medical purposes or employment in the marijuana industry may constitute conduct that violates federal controlled substance laws.”

This can be enough to tip the scales against them in judging whether they have “good moral character.” This means buying marijuana for personal use or even working as a cashier at a dispensary might bar an immigrant from citizenship. They will have to wait up to five years before being eligible to apply for citizenship again.

Similar conflicts even get in the way of international travel. After Canada legalized recreational marijuana last year, U.S. Customs and Border Protection issued a warning to travelers. U.S. officials can now deny Canadians entry if they are going to the United States for “reasons related to the marijuana industry.” Those that work in the industry but are traveling for unrelated reasons won’t get turned away, although using marijuana in a legal state could disqualify them from future entries.

As the legal marijuana industry expands, immigrants seeking to take advantage of the industry find themselves increasingly at risk. USCIS’s guidance is a clear sign that that Congress still needs to act on this state and federal conflict. This will ensure immigrants are not unfairly denied citizenship for partaking in something completely legal in their state.