Yes, federal law trumps state law, however, once enough states change their laws there will be enough support to change federal law. This is how alcohol prohibition was first passed and then later repealed. Also, it is local law enforcement that conducts most of the arrests, so if their mission statement is changed you have fewer jack booted thugs to worry about.
Check out NORML and the Drug Policy Alliance for more information about this.
Cannabis legalization will occur, it is just a matter of time and effort!
Peace!
A scale is a wonderful thing. Everything else posted by CS is lunatic fiction.