“President Barack Obama will sign an order banning federal government contractors from discriminating against gay and transgender workers, officials have said.”
I don’t think he has the power to do that. If he has the power to do that, the next POTUS has the power to ban using any queer government contractors, or one that has any queer employees!
Unless there are people who are willing to stop him, he has the "power" to do just about anything he wants. He may not have the "authority", but he clearly has the "power."