Colorado and Washington state voted in a referendum to legalize marijuana. Not just medical marijuana, recreational marijuana. (Oregon defeated a similar measure.) The problem is, the sale and possession of marijuana are still illegal according to federal law. The states are trying to figure out what to do and how this would work.
What we have is a crisis of federalism. Conservatives, who might normally oppose drug legalization, are in the position of championing states’ rights, while liberals, who might normally favor legalized drugs, are in the unusual position of opposing federal regulation.
At any rate, if the states can figure out how to implement that referendum, Colorado and Washington can expect all kinds of drug tourism. That might not be a pleasant prospect.