House speaker John Boehner warned the president on Tuesday that by the end of the week, he will be in violation of the War Powers Resolution unless American participation in the military intervention in Libya ends or Congress authorizes the mission.

Earlier this month, Congress reminded the president in a resolution that he hadn’t sought approval for his actions in Libya. Sunday will mark ninety days since the operation began — the maximum amount of time granted to the president under the 1973 law to initiate and conduct military strikes.

Boehner had some strong words for Barack Obama in the letter he sent to the White House on Tuesday, suggesting that the president might be in violation of his oath of office unless he respects the War Powers Resolution.

You took an oath before the American people on January 20, 2009 in which you swore to “faithfully execute the Office of President” and to “preserve, protect and defend the Constitution of the United States.” The constitution requires the President to “take Care that the Laws be faithfully executed,” and one of those laws is the War Powers Resolution, which requires an approving action by Congress or withdrawal within 90 days from the notification of a military operation. Given the mission you have ordered to the American armed forces with respect to Libya and the text of the War Powers Resolution, the House is left to conclude that you have made one of two determinations: either you have concluded the War Powers Resolution does not apply to the mission in Libya, or you have determined the War Powers Resolution is contrary to the Constitution.

Nearly every president who has occupied the Oval Office since Richard Nixon’s veto of the War Powers Resolution was overridden by Congress has maintained that the law may be unconstitutional. Ronald Reagan never asked for congressional approval of engagements in El Salvador and Honduras. Congress was out of session during George H.W. Bush’s invasion of Panama and Bill Clinton’s bombing campaign of Yugoslavia during the Kosovo War wasn’t mandated by the legislature either.

President Obama previously missed the sixty day deadline for the regular use of armed forces. The War Powers Resolution gives him another thirty days to withdraw troops. What happens if he ignores that provision as well? Probably nothing. There is very little chance of Congress enacting legislation to end the mission in Libya. Even if Republicans in the House of Representatives would so explicitly seek to defy the president, Senate Democrats could block a bill indefinitely. And if they pass it, Obama could use his veto.