That's the problem! The opinion compares Aereo's use of tiny antennas to cable companies' use of one big one. They argue that since Congress passed a law back

That's the problem! The opinion compares Aereo's use of tiny antennas to cable companies' use of one big one. They argue that since Congress passed a law back in the '70s to define the cable companies' practices as rebroadcast, that law should be read as also defining what Aereo does as rebroadcast.