No? Maybe? Hmmm.

§91.19 Carriage of narcotic drugs, marihuana, and depressant or stimulant drugs or substances.
(a) Except as provided in paragraph (b) of this section, no person may operate a civil aircraft within the United States with knowledge that narcotic drugs, marihuana, and depressant or stimulant drugs or substances as defined in Federal or State statutes are carried in the aircraft.

(b) Paragraph (a) of this section does not apply to any carriage of narcotic drugs, marihuana, and depressant or stimulant drugs or substances authorized by or under any Federal or State statute or by any Federal or State agency.

(c) No certificate holder may allow any person to board any of its aircraft if that person appears to be intoxicated.

What if you were in a state that medical marijuana is approved. You take off, aren't you then in national airspace? Can you land in a state where medical cannabis is illegal? As long as you don't leave the terminal, but is an FBO considered an airport terminal.

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