As 33 states in the US have legalized some form of medical marijuana, one might assume that traveling with it should be relatively hassle-free. But differences between state government rules and those set by the federal government mean that traveling with medical marijuana, if not done right, cold leave you in a complex legal grey area, if not in prison.

Despite its legal status in some states, the federal government still classifies marijuana as a Schedule I controlled substance. This means that technically, anyone transporting it between states is committing a federal crime and thus could be charged for drug trafficking- penalties going up to 5 years in prison alongside a fine of $250,000 for first time offenders.

Although airport staff are primarily focused on finding items that could be dangerous on an airplane, such as sharp objects or explosives, they nevertheless hold they right to search belongings. Then, if they find medical marajuana or other scheduled drugs on a person, they are required by federal law to refer them and their owners to local law enforcement. Should this happen in a state where medical marijuana is legal, it is enough to simply present your medical marijuana card to get away penalty-free. If not however, you may be arrested and charged for drug possession.

Even though almost 20 states now accept out-of state medical marijuana authorizations, as reciprocity laws vary between states, it makes sense to double check the specifics of your destination before traveling there. For example, in some states, such as Arkansas, visitors need to register for a medical marijuana program 30 days prior to travel and pay a $50 nonrefundable fee. Residential status may influence legality- although residents of Oregan may possess up to 24 ounces of marijuana, visitors are only permitted to carry up to an ounce.

Also to consider is that many travel carriers- including airlines, bus lines and train operators- ban the transportation of marijuana on their vehicles, even in the presence of a medical card. Delta Air Lines, Alaska Airlines, American Airlines, Amtrak and Greyhound Lines for example have completely banned transporting the substance for any purpose. Thus, if planning to travel with medical marijuana, it also makes sense to double check with your transport carrier and of course, if driving a vehicle yourself, not drive under its influence.

Sources: New York Times, Transportation Security Administration and WJLA