I think the 4" law just needs to get tossed out, just have regulations on that with every turtle sold the buyer has to be made aware of the potential for salmonella. Of course anything could transmit salmonella, so maybe anyone buying anything should be made aware of it too.
By the way, what do you think of how the laws are written within the states in regard to owning native flora and fauna, I know in Ohio you have to have a permit to own any non-game animals and a fishing license to own any game animals. Even if it's captive bred and you can prove it they want you to have a permit for it, which is unfair in a way.