system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How can Marijuana be legal on a state level while it's illegal on a federal level? Does the federal law mean nothing?

I never understood this. (I am not from the US myself.)
gpt
State and local law enforcement agents have no obligation to enforce federal laws.  They usually do help federal agents out of courtesy and because they more or less agree with the laws the feds are enforcing.  But the federal government has nowhere near enough agents to enforce the law nationally, and they never have.  They have always needed state and local help.

If the state has legalized something that is illegal at the federal level, then the state and local law enforcement agents are going to respect the state and local laws.  They will no longer assist federal agents going after anybody that is behaving legally under state law.

Federal agents *can* still arrest people for possession and distribution of marijuana in those states.  The Obama administration has allowed the DEA to raid medical marijuana dispensaries before.  But now that two states have gone beyond medical marijuana, it's a public relations nightmare for the feds.  Trying to make an example of out an entire state would almost certainly backfire and turn public opinion against the feds.