I'm not a Constitutional expert but to me it doesn't make sense in my mind. As of right now the Federal Government believes Marijuana is bad and should be illegal.
Let me think of analogy, the Federal Government is your Mom. The states are your uncles/teachers/whatever and your just a boy. Should your Uncle/Teacher/whatever have say over what your Mother thinks you can do? No.
That, and it just seems absurd for Federal Government to get spanked around like this aren't they suppose to be the ones in charge?
The analogy does not work.
The United States of America was concieved as a federation of independent states. The Federal government was supposed to be responsible for maintaining interstate commerce and foreign policy. Those are the only roles of the Federal government, as defined in the Constitution. The 10th Amendment of the Constitution states that any role not explicitly defined in the Constitution as the jurisdiction of the Federal government falls to the states to regulate. Ultimately, citizens of the US are beholden to their state laws first and federal laws second. This is why there is no federal identification system and why the subject is so touchy.
So, no, the Federal government is not like my mother and the states are not like my extended relatives.
The Federal Government exists to protect us from foreign threats. The states were made sovereign precisely to protect us from a big, centralized government...which is exactly what we came here to flee. Remember, the Revolutionary War started in large part due to a body who had no idea about the conditions of the colonies determining policy for those colonies. Likewise, people in Washington DC have no clue what conditions are like in California, and thus have no background with which to provide us with policy. That is why we have State governments.
Proponents of the so-called "living constitution" will claim that the founders expected the Federal Government to eventually become a centralized monolithic government, but that's horse shit. Many of the drafters of the Constituion and many of the early presidents wrote specifically that the Constitution was meant to be interpreted literally, and none of the policies contained there-in are as yet outdated. They did, in their genius, leave open a method to change the Constitution, and if the Federal Government wants to expand their power, they must do it with a three-forths agreement by the states.
The bottom line is that the states give power to the Federal Government and they can take it away. State laws supercede any Federal Law except a constitutional amendment.