Another nice example of the same kind of political logic Max and I are talking about in another thread. Everybody wants an all-powerful federal government that will do things for us we don't want to do, like buy us lunch and raise our kids and "provide" us with health insurance and ... I could go on forever probably, but when you open up that door, all of a sudden the tools used to build that all-powerful federal Mommy start getting used abusively, such as sending in the feds to bust medical marijuana outlets and customers in states that have passed laws to make such things completely legal.
In this case, the power to do this hinges on a willfully inaccurate interpretation of the "Interstate Commerce Clause" in the Constitution. Here's a completely unbiased link:
http://www.answers.com/topic/commerce-clause
Read that and you tell me if you can see how those words could be logically and fairly bent to include what's going on in the states that have adopted medical marijuana provisions.
Here's another one: "The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States." That last little bit is what's called the "General Welfare Clause."
http://www.answers.com/topic/general-welfare (a lot more wordy, but interesting if you care)
That clause also has a long history of abusive misinterpretation that props up the federal government's ability to basically get away with whatever it wants. Two very simple amendments to the Constitution could easily clarify the whole mess and most of the problems this country has would be fixed magically overnight... but unfortunately the people of this country would rather use the government guns to get "free" crap without being bothered to earn it for themselves and punish people of whom they don't approve (like potheads.)
Short answer for Noob: Vote Libertarian.