The satellite still needs to be able to receive the signal from the terminal. If the Iranian Government sets up transmitters that send up Noise at the satellites, the satellite isn't going to be able to receive the low power transmissions from the terminal if the jammer is close enough to the terminal.

It depends on the Jamming power and the satellite beamforming how close you would have to be to jam it.

This is not the case for GPS because GPS is receive-only and the satellite doesn't listen for user transmissions (although you could still try to jam the control uplink to prevent synchronization which would decrease accuracy over a few days, but then you would have to be close to the GPS control stations and you'll probably get arrested soon)