I’m an extra class amateur radio operator. There is no law against buying amateur radio equipment, no requirement to have a license prior to purchasing any such equipment. The requirement of the license is to operate such equipment.
As a result, you get (unlicensed) people from time to time that buy amateur radio equipment and go on air. There are also necessary requirements of identifying your call letters every 10 minutes and on the end of your final transmission. More often than not, when (unlicensed) people buy amateur radio equipment with the intention of using it illegally, they have no desire to operate legally either. In fact, they usually behave disruptively or will at least turn to doing so when they find others ‘with’ licenses do not desire to talk to anyone operating without the proper license or that do not follow the proper use of call signs, etc.
It is an unwritten rule amongst hams that whenever someone is being disruptive on the airwaves, not to acknowledge the disruptive broadcast in any way shape or form. The reasoning behind this is, that if someone is trying to be disruptive, acknowledging the transmissions or their disruptive nature alerts the pirate operator that their attempts are being successful.
Most amateur radios are ‘simplex’ – which means they can either be transmitting or receiving but not do both at the same time. This means that someone transmitting has no real indicator if their signal is being received by anyone else – until someone acknowledges hearing it. Thus the unwritten rule.
When someone ‘trying’ to be disruptive is ‘acknowledged’, they will continue so long as they know their attempts are successful. If they think there is something wrong with their transmitter or they aren’t doing it right, they give up and stop trying in the future.
There is of course an exception to this. This is when someone has a pseudo-doppler or phased antenna array system that can pin-point the transmission point. In that case, they generally coordinate with other hams on another frequency and acknowledge the signal just long enough to triangulate to report it to the F.C.C. – then go back to ignoring it. (i.e. – if someone is actually ‘able’ to do something about the pirate operation)