It's interesting, because contracts revolve around players being 'registered' to clubs.
If the clubs are no longer sanctioned, technically the players are no longer registered because they haven't signed contracts for a different competition. It's why free agents can sign outside transfer windows as they are unregistered, so can register whenever, whereas others can only move at pre-selected times.
So, in theory, every player at these Super League clubs, if the clubs are 'deregistered', would have to sign new contracts with their clubs in relation to the Super League, but would be free to move to another UEFA-sanctioned club because the players are 'deregistered'.
Whether that'd hold up in court... pfft. Dunno.