system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When the U.S. Government says "You can't sell pot" the individual States can decide "Oh yes we can!", but when the Feds say "You must allow gay marriage" why aren't the States aren't allowed to say "No!"

I'm pro gay marriage by the way, congratulations everyone!!
gpt
So there are two things at play here.  Federal laws superiority over state law, and the government utilizing its ability to prioritize where it spends its limited resources.

So when the federal government says possession and sale of pot is illegal.  It absolutely is illegal and if you were arrested for it, even in a state that legalized it, you would absolutely be found guilty and punished under federal law.

But the thing is the only way that happens is if someone actually arrests you, and since the states decided they weren't going to participate in enforcing that particular federal law the federal government hasn't really bothered to put in the effort to do it themselves.  Just because something is illegal on the federal level doesn't mean state officials must arrest people for it.  ~~They're allowed to~~ (Edit: It looks like they're not normally allowed to, thanks for the correction!), but it's not required.

On the other hand we have gay marriage.  States already perform marriage, they're in the marrying people game. The supreme court effectively said you're not allowed to refuse marriages to people who want to marry someone just because of their sex.

The difference here is that if the states don't enforce federal pot laws, there aren't any victims who can sue.  Who is harmed by not being arrested?

But the states **must** not discriminate in marriage anymore, if they do individuals would be able to sue and the courts would compel marriage officials to perform the act, or send them to jail.

The main bit is, no one is a victim when states refuse to enforce federal drug laws.  But there would be victims if states refused to follow the Supreme court ruling on same-sex marriages.