I'm pretty sure it's not legal, either, but in the last thread on this subject where I quoted the relevant section of the relevant law, one guy just repeatedly mouthed off that I was wrong until another finally came up with some actual case law.
It appears to be an offense on paper that doesn't get successfully prosecuted.
To add to what webstar22 posted. Unless the FCC has changed its rules and regulations, it IS illegal to profit from monitoring radio communications unless you have the permission of the license holder. The fine is rather stiff but the rule isn't enforced much. It pretty much takes a complaint from the license holder before the FCC will do anything.