I'd hardly call it a minefield. Most of us are citizens of just one country (although some can play the dual or triple nationality game) and that gives us only one legal avenue for radio licensing. Ditto for the title/flag on the boat.
And then you operate under that one set of restrictions, which INCLUDE reciprocity agreements with other nations. And you follow those terms when operating in another sovereign's waters. When there's no reciprocity, you still follow that other sovereign's laws. For radios, pollution, contraband, and everything else.
No big deal, you just need to do your homework ahead of time.