I keep hearing in the news about how preserving "states rights" are really important and that the federal government shouldn't overreach. I don't quite understand why states rights are important though -- why shouldn't we have a uniform set of laws in the country mandated by 1 government (e.g. the federal one)? For instance -- its very confusing how certain states have legalized things (e.g. marijuana) but the federal government hasn't, so a state trooper wouldn't be able to charge you with possession but the DEA could.

Can someone explain or point me to some good articles explaining this? I feel like this isn't something that is emphasized in Canada so I don't really have any context for it.