From what I've seen there's some dispute between right-libertarians as to whether centralization is ever OK. Rothbard said no, while Walter Block made the claim that the fear of Federal expansionism of power didn't matter, that if an action (Since he was an ancap, that would be simply the repealing of a lower-level action) was justified, it didn't matter who did it. I can certainly see the merit of both sides, but to claim that just becasue you give the Federal government the power it will use it the way you want it to is a mistake. If the Federal government can legalize anything nationwide, it can also illegalize it nationwide. Decentralization does nothing more or less than making tyranny easier to escape.
Hence why, I, and I believe Ron Paul as well, support it.