With 36 states plus Washington, DC, now allowing the use of marijuana for medical purposes, many in the minority of US citizens without legal access to medical cannabis in their own state wonder if it’s possible to bring cannabis across state lines.

In short, it’s not. As long as medical marijuana remains illegal at the state-level, it will be illegal to use it regardless of where it was purchased or if the individual concerned holds a valid medical cannabis card in another state. Doing so could result in arrest and a charge for possession.

Then there’s the added issue of federal law, under which cannabis is still illegal for all purposes, including medical. This means federal agents have the authority to arrest individuals who are using medical marijuana in accordance with state law, but in practice this doesn’t happen owing to a federal rider prohibiting the Department of Justice from using federal funds to intervene in state’s medical marijuana programs.

But crossing state borders with legally purchased medical marijuana is another matter as this can be considered drug trafficking under federal law. This can result in a lengthy prison sentence and a fine of up to $250,000, depending on how much cannabis federal agents intercept. The same holds true when traveling by airplane. When passing through an airport, passengers are subject to the Transportation Security Administration’s (TSA) authority. The TSA, as a federal agency, is instructed to report violations of federal cannabis laws to local, state or federal authorities if marijuana is found during a security screening, no matter if the state concerned has legalized the use of marijuana.

Despite cross-border cannabis restrictions, some states with medical marijuana programs allow out-of-state individuals to apply for a medical cannabis card that can be used in-state. While the registration process varies from state to state, this typically involves a physician’s recommendation alongside administration fees.

As this process can be complicated and expensive, many patients living in prohibition states who want cannabis for medical purposes travel to a state where the use of recreational marijuana is legal. Otherwise known as “marijuana tourism,” this is perfectly legal for out-of-state patients to do, so long as they don’t try to take it home, but some legal states limit the amount of cannabis non-residents can purchase.

With more and more states reforming their cannabis laws in their own way and in opposition to the federal government’s prohibition, the legal landscape for cannabis users can be confusing. If you are unsure about the law concerning your use of cannabis, then you should contact a lawyer.