During the Bush Administration, there were four advocates for the strong Unitary Executive theory on the Supreme Court, namely Justices Scalia, Roberts, Alito and Thomas. They advocated for broad powers for the President, especially in time of war, within the Executive Branch. Bush, indeed, depended on this theory when he issued all those signing statements as well as the legality of contravening written U,S. law with allowing torture as an instrument of the U.S. Government.
Despite the fact that Executive Orders,on immigration issues, having gone unchallenged during the Administrations of Ronald Reagan and both Bushes, a lawsuit challenging the right of Obama to issue and Executive Order, on immigration, is pending resolution.
The outcome of that case may also determine whether only white Presidents may authorize torture or offer Executive leniency to migrants.