While state laws are beginning to change, federal law has not. It’s still illegal on the national level, and so marijuana is banned from any federal property or areas under federal control which means the screening areas in airports and on airplanes. So even if you stash your stash in your checked luggage, you’re violating the law. Nor can you ship marijuana home legally.
And federal law makes no distinction between medical marijuana and marijuana used for other purposes, so even if you have a medical prescription, don’t expect to find much sympathy if a TSA agent stops you while going through security.
TSA agents are not law enforcement officers, so if they find marijuana in your carry-on luggage—which, by the way, they aren’t specifically tasked to look for—they’ll turn the situation over to a local law enforcement officer.
Travelers coming in the US, however, are banned from bringing in marijuana or any articles intended to be used with grass.
You’ve been warned.