An increasingly desperate LightSquared today accused the Federal Communications Commission of violating its constitutional property rights by rejecting its application to build a 4G network on spectrum adjacent to that used by GPS devices, and demanded that the FCC either reverse its decision or give LightSquared a new chunk of spectrum.

The bold claims follow the FCC's decision last month to withdraw LightSquared's conditional approval to use spectrum allocated for satellite transmissions for cell towers instead. In a long response to the FCC that was made public late Friday, LightSquared claimed the FCC's action constitutes a "taking of LightSquared’s property without just compensation in violation of the Fifth Amendment of the Constitution."

The argument seems unlikely to sway the FCC. The agency has authority over how spectrum is allocated. Moreover, the FCC made it clear to LightSquared in its conditional approval that a final waiver would not be granted unless concerns about GPS interference were eliminated.

LightSquared still disputes the results of government-funded studies that showed interference with GPS devices, but says it will settle for an alternative: a gift of spectrum from the US government. Assuming the FCC's most recent decision is not overturned, LightSquared says the FCC should "identify and engineer a partial or total exchange of alternative terrestrial spectrum rights, which could be used without any impact on existing GPS receivers."

With LightSquared's cellular prospects looking increasingly dim, the company recently bolstered its legal staff by hiring Bush v. Gore lawyer Theodore Olson, as well as former Department of Labor Solicitor (and son of a Supreme Court Justice) Eugene Scalia. There has been talk LightSquared might run out of money within a year or less, but it now has $65 million in new funds from its breakup with Sprint. If LightSquared doesn't get what it wants from the FCC, a lawsuit against the agency could follow.