If the voters of California legalize marijuana for medical use then the federal government, in other words, has no business arresting California's law abiding citizens. Meese's views are shared by many in the legal profession. Diverse state law is a good way to discover the best approaches to dealing with all kinds of public policy. Wisconsin's pioneering efforts taught the nation that workfare was a viable alternative to out failing system of welfare. We should not disrupt similar experimentation in dealing with marijuana.
Diversity is also a good in and of itself.
Federal law enforcement has an important role to play when criminals try to escape prosecution by fleeing across state lines. Purely local matters, however, should be handled locally. Recently, conservatives rightly argued that the 55 mph speed limit might be right for New York but not for less-populous North Dakota. Decentralization not federalization of speed limits, they said, is the correct policy. Principled conservatives will acknowledge that the same argument holds true for medical marijuana.