If I want to take a flight from one US state where Marijuana is legal for recreational use to another one where it's legal for recreational use, can I take some small amount of Marijuana with me in the checked luggage?
From the TSA website:
Possession of marijuana and cannabis infused products, such as Cannabidiol (CBD) oil, is illegal under federal law. TSA officers are required to report any suspected violations of law, including possession of marijuana and cannabis infused products. TSA’s screening procedures are focused on security and are designed to detect potential threats to aviation and passengers. Accordingly, TSA security officers do not search for marijuana or other illegal drugs, but in the event a substance that appears to be marijuana or a cannabis infused product is observed during security screening, TSA will refer the matter to a law enforcement officer.
Albeit with the law enforcement response, it's treated like anything else that TSA doesn't allow on board an aircraft.
While TSA isn't looking for cannabis specifically, if they find it, they will call in the local law enforcement, who will check that you have less than the legal limit in your state, and send you on your way. But you'll have to get rid of it before you will be allowed through the checkpoint.
Some airports are beginning to set up so-called amnesty boxes where people can dispose of their cannabis or other drugs before going through security screening.