It doesnt matter if the NFLPA and the owners agree on this. All it would take is a court order stating that the NFL doesnt have the right to change a contract and then enforce it on prior acts which is exactly what they did.
And if you cannot see how this is simply Goodell bowing to the press by hammering Henry and Jones while ignoring Porter and Johnson i do not know what to tell you.
Im not saying that Jones and Henry dont seserve punishment but i will say that equality is much more important in a free society that youre need for revenge through punitive action.
They might get away with it but that does not make it right in any way shape or form.