Back in 1857, part of the Dred Scott decision claimed that slaves could be taken into all the Territories (slave or free) due to the 5th amendment's provision that private property could not be taken from a person unreasonably (in that horrible case, slaves). That is, if I travel from a slave state with my legal slaves, then they are still my property when I travel to any other territory or state.
So if I buy some mary jane in either Washington or Colorado, shouldn't I be able to take it to all the other states without it being confiscated? Otherwise my 5th amendment rights are being violated, according to Dred Scott?
(I love the concept of taking a horrible law and twisting it to progressive uses...)