If we're talking about IBM/Red Hat here, they are not exercising their rights.
Can they close the SRPMs? Yes they can.
Can they tell "You can't redistribute this GPL licensed source code", haha, no. They can't even tell you to not redistribute BSD/MIT/Expat/WTFPL[0] code. They can't override these legal texts with EULAs.
GPL is working as intended, and irritating corporations the way it should, and yes, what Red Hat done is treason, not because they closed the SRPMs, but the collective things they did.