That would be a question for the LAPD. But, as long as the radios are receive only on their freqs, I don't think there is much they can do with these people as far as that is concerned.
...and if those radio's were programmed to tx on LAPD channel's that also a crime...
Actually, the radios could be
configured for transmit as well. As long as the radio
doesn't transmit, no crime has been committed. I suppose a clever prosecutor could
attempt to prove
intent by showing the radios were configured for xmit, but that would open up a lot of ancillary issues involving equipment search and prosecutorial authority since communication law is the sole prevue of the Feds.
It's a bit like having a vehicle that
can cruise at 100+ MPH. As long as the driver adheres to the speed limit, there's no crime.