To expand on the analogy, it's more like GPS receivers have a very wide funnel so that they catch every drop. This funnel extends into the range that lightsquared has. If it weren't GPS, the FCC would just say "fix your damn receivers, they are within the parameters of your license" but GPS is clearly Sui Generis because of the combination of the weakness of the signals and the importance to our infrastructure.
The problem isn't the noise, it's the volume. The volume alone would overwhelm the GPS filters' ability to filter out the out-of-band noise.