This doesn't appear to be accurate. Most of the cattle is sent to the mainland due to a lack of slaughterhouses, not due to any law restricting said slaughterhouses.
That is not what I was told at parker ranch! Or possibly I misinterpreted what they said. Thank you for the clarification. I do think that the overall result is more or less the same, instead of being an absolute ban, it's a licensure restriction that limits the number of cows that can be slaughtered locally.