>I think it's up to 16 or 18 states now. I was wondering what happens (if anything) when it gets to beyond 1/2 the states in conflict with the federal law?

The feds already know enough to not interfere with the states.

If they interfered, they'd be taken to court and made to look like idiots for violating the 10th amendment, therefore, they avoid kicking the wasp's nest.