I parsed that as:

> HAMs are typically empowered [in their rule-following] by actual telecommunications agencies [who have] legislative authority to enter premises and what have you to resolve issues

That is, hams (not "HAMs") feel empowered to advise others to obey the law, because they have to work with government agencies who can make life unpleasant for those who don't. It's not "hams [have] legislative authority".

Maybe I'm wrong, but that's how I read it.