Actually, a good example would be the Debt Ceiling. He can't raise it on his own beyond the limit established by the Congress, but there is no actual floor. Accordingly, if Obama decided tomorrow to unilaterally LOWER the Debt Limit, Congress would have to pass an Amendment to block him. Of course, He would raise all sorts of sand if he did something like that, but he couldn't be impeached for it. Likewise, he is free to rearrange the spending on items that don't have specific allocations established by Congress, and he could reallocate funds from a program that everyone agrees is ripe for disestablishment to another program, or direct to the General Fund. Congress has absolute control of the Budget, but the President can move things around as needed. If tomorrow the Army and the Marine Corps declared that they no longer needed - or wanted - Tanks, on Obama's Executive Order they could turn them over to the General Services Administration for proper disposal, and apply the funds appropriated for their maintenance back to the General Fund. Congress might have a fit, but there would be nothing they could do about it. An example of this is the Beret. Prior to President Kennedy prescribing by Executive Order the Beret for the Army's Special Forces Groups in 1963, and the spending funds otherwise allocated to other Military purposes for its addition to the Authorized Clothing Bag, the Beret was universally banned in the US Military. Ultimately, many other US Military personnel wear one today, and there has been no political rancor.