President Obama’s vetoes earlier this month of two bills that would have blocked administration efforts to blunt climate change surprised no one. The vetoes came after Congress passed resolutions that even Republican leaders admitted were largely symbolic — precisely because the GOP lacks the votes to override Obama.

By choosing an unorthodox and unnecessary method to exercise his veto, though, Obama may have handed a major victory to the Republicans by providing them with a way to challenge the constitutionality of his action. Here’s how.

The Constitution provides the president with two veto options: the regular or return veto, where the president returns the bill to Congress with his objections; and the pocket veto, which kills the bill without returning it to Congress. Presidents like the pocket veto better for the obvious reason that it is absolute, with no possibility of veto override, but the Constitution does not allow presidents to pick and choose the kind of veto they wish to use. The regular veto is unconditional as long as the bill can be returned. But the pocket veto, under the terms of Article I, Section 7, has two conditions for its use: Congress must be adjourned, and bill return must be “prevented.” These two linked conditions in turn acknowledge the existence of adjournments when bill return is possible.

In fact, the return veto is actually preferred by the terms of the Constitution, as was the clear intent of the Framers. We know this because at the Constitutional Convention, they repeatedly and emphatically rejected a monarchical absolute or non-override veto for the president. The right of Congress to have a final chance at vetoed bills was essential to the checks and balances system they created.

Yet the pocket veto is absolute in its effect, because the bill dies without return to Congress, so how is its presence in the Constitution explained? The answer is that the pocket veto was created to prevent Congress from ducking a veto by passing a bill and quickly adjourning to prevent the president from returning the measure. Without the pocket veto, an objectionable bill would simply become law after ten days, whether the president signed it or not.

So how can a regular veto be used if Congress is not in session, which it is not, since the first session of the 114th Congress ended Dec. 18? Simple: Each house designates legal agents to receive veto messages and other communications. This routine mechanism has been used thousands of times by Congress for decades during long weekends, vacations and breaks, just as the White House receives bills from Congress on behalf of the president when he is absent or indisposed. Both procedures have met constitutional muster. As the Supreme Court said in 1938, the “Constitution does not define what shall constitute a return of a bill or deny the use of appropriate agencies in effecting the return.”

In his two vetoes, Obama issued a so-called “protective return pocket veto,” whereby he announced a pocket veto and titled his veto message “Memorandum of Disapproval” (the name for a pocket veto message). But he then proceeded to return the two bills to Congress — a return veto. The justification for doing so is always the same: to “leave no doubt that the bill is being vetoed.”

The problem is that this gambit creates doubt because it combines two mutually exclusive actions: a regular veto and a pocket veto. Even more troubling, the history behind this veto mashup — claiming the exercise of a non-return pocket veto while simultaneously returning the bill to Congress — is a presidential power grab designed to stretch the no-override pocket veto into an absolute veto that could be used whenever Congress is not in session, giving the president the very power the Founders sought to deny the office.

This practice traces to former President Gerald Ford’s administration, when the president issued five such dual vetoes. Then-Sen. Edward Kennedy challenged these vetoes in federal district court, where he prevailed. Ford halted the practice and agreed to use a pocket veto only at the end of a two-year session of Congress. Yet the practice was resuscitated by President George H.W. Bush, who claimed to pocket veto two bills that he also returned to Congress. President Bill Clinton did the same thing three times in 2000, and President George W. Bush employed the practice once in 2007. Obama, meanwhile, has used the maneuver five times out of seven total vetoes.

The Republicans’ option is clear: Sue the president, arguing that the vetoes were facially unconstitutional because they combined two mutually exclusive procedures, and because Congress had designated legal agents to receive veto messages. Since Obama withheld his signature, the two bills, instead of being vetoed, should have become law without his signature after ten days.

It would pain me to see Obama’s laudable efforts to reduce greenhouse gases thwarted. But it is even more painful to see this constitutional Rube Goldberg veto device persist. Obama could and should have simply exercised the return veto, but he didn’t. It’s time to bring this practice to an end. Maybe it will take a legal victory by the president’s opponents to persuade him.

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