There will be a Republican President again someday. This will happen. Democrats, having forgotten that fact, would do well to remember it. Suppose this happens too: Congress cuts taxes, stating in the preamble to the law that it intends to spur economic growth and, Laffer-style, boost revenue. The cuts fail to achieve that goal, so the President—on the grounds that a law should not be implemented in a manner contrary to its stated overall purpose—unilaterally orders the IRS to cut them some more.
After the arguments made to the D.C. and Fourth Circuits to justify the subsidies for coverage on federal Obamacare exchanges, the howls of indignation might be hard to separate from the howls of righteous vengeance. Because while the tax-cut scenario takes the case to eleven, the species of argument is the same: that the President is authorized to violate—or, more politely, let us say, reconceptualize—the letter of a law in the name of achieving its overriding purpose.