I wonder, would they have been able to arrest him if he was shooting video within the security area? Is it legal to record the audio of a cop if you inform them

I wonder, would they have been able to arrest him if he was shooting video within the security area? Is it legal to record the audio of a cop if you inform them about it first? I need to read up on this before I need to travel again. Someone should create a know your rights quick reference guide for air travel. Side note: I flew from HK to SF yesterday.. No backscatter machines on re-entry of the US border. When I flew from SFO to HK a couple of weeks ago I was lucky enough to have made it into a line that was only a metal detector. They did have some backscatter machines in place. Second side note: On my flight home from HK to SFO they had roped off the waiting area at my gate. There were about 6 Muslim men (hats, bears, speaking arabic gave me this impression) waiting in line with the rest of the passengers to get all of our carry on items physically searched before our flight. I'm sure the extra screening was not due to their being on the flight /sarcasm. I over heard some of the men speaking about how they can fly anywhere in the world and don't have a problem. But as soon as they fly to the US, they get harassed up and down. I truly felt sorry for them.