Yup. State don't have any power to refuse directly. Once in a
   state, a state _can_ deny services and do other awful
   non-federal regulated practices, but they can't be denied
   'border crossing' because US state borders are weak things.
   That's also one of the things that makes our setup very
   powerful, as opposed to 50 independent States loosely knit
   together. Momma USA gives a lot of power to its children, but
   the states remain children for a good reason. It works.