And Nevada can tell them to take a flying leap, refuse to acknowledge their status from Maine. Some states do that.
It's a people's fight - not the government's.
No, Nevanda will not be able to legally do that. Because of the Full Faith and Credit Clause in the US Constitution, other states are legally bound to accept marriage certificates from other states, even those certificates from homosexual married couples coming in from another state where the practice is legal.
Now, Congress can try and slip in some sort of exception clause in the Full Faith and Credit Clause, or they could propose an amendment, defining marriage as being between one man and one woman. The first scenerio is more likely than the second, and probably neither of them will ever happen.