Canadians with a Nexus Card who use marijuana might want to be extra careful crossing the US border after a leaked memo says if guard finds out about it, the pass can be taken away or not granted in the first place.

Global News has released a set of instructions that were intended only for high level US border guards regarding Nexus travelers and cannabis. The instructions list 30 different cannabis-related scenarios including prior drug use, operating a grow-op and having a valid medical marijuana card. The follow-up actions are blacked out.

As Global News reports, since U.S. law assumes that any level of use of controlled substances like cannabis is “abuse,” there have been concerns since legalization that it could be used to ban any Canadian cannabis user, no matter how occasional their use was.

The document says the instructions were developed in order to assist managers in the field regarding Canada legalizing marijuana and are meant to be a guide. However, the practical implications of marijuana in Canada could lead to a potential increase of inadmissible travelers arriving from Canada.

The instructions go onto say that there are no marijuana use based questions during a Trusted Traveller eligibility interview, however travelers “who are found inadmissible due to a controlled substance violation or admit to the use of controlled substance would not be eligible to participate in a Trusted Traveller Program such as Nexus.”