Basically, the premise is that the FCC hands out licenses to radio stations giving them exclusive rights to a frequency over a territory. That's the way it's been for a century and they've created a delicate balancing act based on atmospheric physics. The FM band, at this point, is practically full. There are a few open spots here and there but there's very little room to squeeze in additional stations anywhere. The AM band still has a lot more room but that one is falling out of favor for a number of reasons. Shortwave even moreso, though a large portion of that band is reserved for ham users anyway.
Pirates, on the other hand, try to wedge their way onto the dial (usually the FM dial). Unfortunately, the way it is with the FM band being nearly full, anyone who tries to squeeze in is almost certainly going to interfere with another licensed station.
Here's the problem with the FCC's law: it doesn't go after the pirates themselves. (Not to mention that property seizure without due process is blatantly unconstitutional.) It goes after property owners. So, say a guy puts a mobile home in a trailer park and operates a pirate station there. The FCC, under this law, is able to fine the trailer park owner who has nothing to do with the pirate broadcast into the millions of dollars, millions that that owner may not have. It punishes someone for a crime they didn't commit, without a trial or prosecution.
