Reports Hit & Run:
Today Nebraska and Oklahoma sued Colorado, arguing that marijuana legalization there is having spillover effects on neighboring states and should be reversed because it violates federal law. The two states are asking the U.S. Supreme Court to declare that Amendment 64, the legalization measure that Colorado voters approved in 2012, is "unconstitutional and unenforceable under the Supremacy Clause" because it conflicts with the Controlled Substances Act.
Make sure to look at background information, especially on the Supremacy Clause, in this article entitled Nebraska and Oklahoma Sue Colorado.
And The Washington Times reports here.