Since when is Obama the United States Supreme Court? He is sworn to protect and defend the Constitution, not interpret it. That Constitution reads:
Article 2 - The Executive Branch
Section 3 - State of the Union, Convening Congress
He shall from time to time give to the Congress Information of the State of the Union, and recommend to their Consideration such Measures as he shall judge necessary and expedient; he may, on extraordinary Occasions, convene both Houses, or either of them, and in Case of Disagreement between them, with Respect to the Time of
Adjournment, he may
adjourn them to such Time as he shall think proper; he shall receive Ambassadors and other public Ministers;
he shall take Care that the Laws be faithfully executed, and shall Commission all the Officers of the United States.
It does not say that he can enforce only the laws he agrees with. I guess the next conservative President can decide not to defend challenges to Roe v. Wade and you will be ok with that.
If you don't like a law there is one constitutional way to change it. Pass a bill repealing it in the Congress and have the President sign it.