gnow,
Jim is quite right this will depend on what the MEL has to say about the malfunction in question. Generally in the North Sea the MEL's are written in a way that you cannot depart an offshore Rig with an MEL defect that would prevent it. This is also true if the helicopter has been rotors running on the deck.
However in conjunction with the aircraft manufacturer special permission for a return can be granted if it is deemed appropriate.
Woolf