Here’s a link to the federal government’s website which state’s it’s a controlled substance and illegal:
http://www.whitehouse.gov/ondcp/federal-laws-pertaining-to-marijuana
Department of Justice Guidelines:
The Department of Justice (DOJ) issued guidance for Federal prosecutors in states that have enacted laws authorizing the medical use of marijuana under state law. The guidelines explain that it is likely not an efficient use of federal resources to focus enforcement efforts on individuals with serious illnesses who use marijuana as part of a recommended treatment regimen consistent with applicable state law or their individual non-commercial caregiver. However, persons who are in the business of cultivating, selling, or distributing marijuana, and those who knowingly facilitate such activities, are in violation of Federal law, and are subject to Federal enforcement action, including potential prosecution.
What that says is pretty much to not bother the people who have a medical use for it in states which have “legalized” it. But if it’s not medical use, to arrest and prosecute.