The congruence between Federal and state laws relating to marijuana, 2 which has existed for generations, is unraveling. In recent years a number of states have reduced or eliminated criminal penalties for the possession or use of small amounts of marijuana;3 twentythree states have established a state law exception for medical marijuana; 4 and Colorado, Washington, Alaska and Oregon now authorize the retail and personal growth, sale and possession of marijuana as a matter of state law.5 Maryland has lately joined the list of states purporting to create exceptions or safe harbors for those wishing to engage in the manufacture, distribution and use of so-called “medical marijuana.”6 Yet Congress’s operative expression of the federal legislat...