By that same logic, making a lot of things illegal is a waste of time. Afterall, no matter how hard we try some tinpot dictator out there will commit war crimes. No matter how illegal we make it, slavery will still happen! Then there is murder... afterall, that is what chytrid does to amphibian populations.
Chitrid is really nasty for frogs. Because of it, many of the frogs in Central America, as well as most of the ranids native to the pacific north west are extinct or on their way there. If we cannot tell ourselves that we need to curtail its spread, then we have no justification for having any environmental law whatsoever. Afterall, Chytrid was spread to the new world by hobbyists and biopharmaceutical companies.
These rules can be enforced the same way laws dealing with livestock are. The infrastructure is already in place it just needs to be expanded a bit. You will still have small scale illegal shipping by private individuals, but that is nothing like the commercial interstate transport that occurs right now. This will also encourage captive breeding, not curtail it. This is because it will become increasingly difficult and thus costly to collect amphibians commercially.
The whole reason dendrobatids are captive bred now is because they were being driven to extinction by commercial collection and habitat destruction and the cost to get them became so high people started breeding them.