It's also not something that you can really stop people from doing.

You might be able to stop people sharing the information freely, but, the transponders that people track and the protocols and standards for the communication are well known internationally. It doesn't take more than $50 in parts to set up your own receiver and connect it to a computer.

I'd consider any law prohibiting the observation of air traffic by the public to be impossible to enforce. How can you stop someone from listening by law?

Sharing the information, however, that's a bit different.