short answer today is "No" pot use is illegal under federal law, notwithstanding some recent judicial qualifying of that principle. I like to think the founding fathers did not care until your marksmanship was expected when the British were massed for an attack and who had confidence in an always stoned Minuteman?

Fellow patriots expected better.... And, as to today's concealed carry and a gunfight, try admitting in court you were stoned when you killed an assailant, and escaping civil liability...you will be liable!!!