I hear a lot that a criminal's confirmed drug use won't help a lot at trial, but I don't buy it. The fact is, as soon as the police officer cites suspected evidence for drug use as among his observations leading up to the questioned shooting, any corroborating (or contradicting) evidence is likely to be admitted.
Ok, so back up a bit. First off, that is not why the car was stopped. It wasn't for suspected intoxication of any sort. And at no point was any mention made of drug use. So introducing that as a factor, after toxicology comes back and says, "by the way, we found some THC in his blood," would be dismissed, and would possibly be grounds for a perjury charge against the officer. (Introducing a brand new "observation" from the scene that doesn't show up in the initial report but just so happens to coincide with a later toxicology screen would be laughably transparent.)
And even if a detail like that is excluded from trial, it is still relevant in contradicting the narrative portrayed in the liberal media that the victim of the shooting was an innocent, law-abiding gun owner.
Why is THAT a good thing? While I don't want to pre-judge the trial of Officer Yanez, from what I've seen there isn't anything in this shooting that seems good or right or acceptable to me. I see someone who appears to have held a license to carry a firearm, who tried to disclose that information to the officer who stopped him, who (again, as near as we can tell) didn't actually threaten the officer, and who was shot dead. While I'm in no way saying that Castile handled himself according with our best practices theories as to interacting with the police while armed, that's not really a responsibility that rests on his shoulders. The officer is the one responsible for everyone's safety when he stops someone, and he ended up shooting someone who was (as far as he could POSSIBLY have known in that instance) legally armed and who very certainly meant him no harm.
So yeah, the fact that he might have smoked a little weed doesn't really put him in the class of lethal criminals who should rightly end up with bullet holes in them. If that doesn't make him a "law-abiding" gun owner, he wasn't apparently any kind of violent criminal, so we need to be pretty careful in attempting to paint him as a member of the criminal set just so we can either avoid putting appropriate scrutiny on the officer, or as a knee-jerk reaction against the "liberal" forces who we don't like for whatever reason.
I see the shooting as something that could have happened to any of us who carry a weapon, and his bit of pot use doesn't separate P. Castile far enough from me for me to feel comfortable dismissing him and excusing his death because he's not like me.
Marijuana use disqualifies one from legal purchase, ownership, and possession of firearms in most jurisdictions.
In ALL US jurisdictions, seeing as that's federal law.
However, it is also a very common "crime" on the cutting edge of a major social change toward legalization, to the extent that some of the states have removed their own laws against it's use. While we understand the concept of the hierarchy of federalism and that the wording of federal firearms law means that marijuana use means you cannot answer a form 4473 truthfully and be sold a gun, this is controversial disputed ground around the nation. At any rate, IF Mr. Castile had said, "Officer I have a permit to carry a concealed weapon and am carrying a firearm now -- AND I want to let you know that I smoked pot yesterday..." that STILL wouldn't be grounds for shooting him, and wouldn't offer support for the necessity of having done so. That information might, possibly, have lead to his arrest, but it isn't an act of violence.