In studying for my Criminal Law final I ran across a delicious nugget in a concurrence authored by Justice Stevens, with whom Souter and Ginsburg joined. The case was United States v. Oakland Cannabis Buyers' Cooperation.
"The overbroad language of the Court's opinion is especially unfortunate given the importance of showing respect for the sovereign States that comprise our Federal Union. ... particularly in situations in which the citizens of a State have chosen to 'serve as a laboratory' in the trial of 'novel social and economic experiments without the risk to the rest of the country.'"
The lesson from the Left: when you like the policy, federalism is great; when you don't, create a constitutional right.