Since Kovalchuk isn't 'under contract' i doubt he is eligible for the expansion draft.
If he were to sign a contract with the Devils, and they didn't give him a NMC and left him exposed, i suppose hed fall under the same rules as anyone else.
That being said, as a lot of people here have said, this is really a one-off situation and NHL could make a call either way, if it were to happen.