That's a red herring. Border control is properly a matter for the Feds, falling under national defense and therefore being specifically enumerated in the Constitution.
You also illustrate the problem with the Commerce Clause. Defined broadly enough, there's nothing that the Feds can't usurp from the states.
I think th 10th ammendment is often exercised by the people (people being plural) of various states (states) being plural.... elect represenatives who decide what laws they want to live by. Both on a local and federal level.
So what laws do you think the states have a right to make? Are there any matters that you think the states have a right to decide, or does the federal government always get to trump the states?
http://wid.ap.org/scotus/pdf/03-1454P.ZD1.pdf
The majority holding:
http://wid.ap.org/scotus/pdf/03-1454P.ZO.pdf
Scalia's concurrence:
A better argument: in general, states shold be able to set their own policy in any area that does not prevent other states from choosing differently. If Arizona were to start letting illegal aliens in without restriction, the right of neighboring states that may wish to set different policies would be infringed. But one state allowing patients to grow their own wacky weed, no interstate commmerce involved, does not affect the right of neighboring states to be more restrictive.