Comment by jjtheblunt

That's probably exactly the rationalization for this. No expectation of privacy in a public space, and therefore no requirement for warrant to eavesdrop. I may not like it, but the government will find absolutely any way to do things we don't like in spite of the infinite attempts to restrain it from doing so decades or centuries ahead of time.

There are eavesdropping laws specifically about audio recording. Not sure if it's federal or state by state.