Bruce Ackerman is a professor of law at Yale and the author, most recently, of “The Decline and Fall of the American Republic.”

CIA Director David H. Petraeus is asking the administration to expand the bombing campaign in Yemen. If President Obama approves this request, he will be breaking the legal barrier that Congress erected to prevent the White House from waging an endless war on terrorism.

Just days after the Sept. 11, 2001, attacks, Congress authorized the use of force against groups and countries that had supported the terrorist strikes on the United States. But lawmakers did not give President George W. Bush everything he wanted. When the White House first requested congressional support, the president demanded an open-ended military authority “to deter and preempt any future acts of terrorism or aggression against the United States.”

Even at this moment of panic, Congress refused to hand Bush a blank check: “Given the breadth of activities potentially encompassed by the term ‘aggression,’ the President might never again have had to seek congressional authorization for the use of force to combat terrorism,” David Abramowitz, chief counsel to what was then the House Committee on International Relations, wrote in a Harvard legal journal in 2002. Congress’s final resolution eliminated the offending language and authorized the use of force against groups and countries that were involved in “the terrorist attacks on September 11th.” The effect was to require the president to return to Congress, and the American people, for another round of express support for military campaigns against other terrorist threats.

The Petraeus proposal, reported this week by The Post, assaults this fundamental principle. Up to now, the CIA’s drone campaign in Yemen has kept close to the legal line by restricting strikes to terrorist leaders, like the American Anwar al-Awlaki. Such leaders may have had personal links to the original al-Qaeda group, based in South Asia, that targeted New York and Washington in 2001. But now Petraeus is seeking permission to expand bombing raids whenever there is “suspicious behavior” at sites known to be controlled by a terrorist group — al-Qaeda in the Arabian Peninsula — that did not exist on Sept. 11.

Before the death of Osama bin Laden, it would have been plausible for the administration to suggest that the al-Qaeda terrorists in Afghanistan and Pakistan were giving orders to the group’s namesake in Yemen. But al-Qaeda’s failure to replace bin Laden with a credible leadership structure underscores the fact that the Yemeni group is on its own. In fact, The Post reported that the administration is weighing expansion of the CIA program precisely because it considers Yemen to pose the world’s most serious terrorist threat.

The risk of attacks from Yemen may be real. But the 2001 resolution doesn’t provide the president with authority to respond to these threats without seeking further congressional consent.

Congress hasn’t reversed itself in the years since it authorized the use of military force. While lawmakers recently elaborated on the president’s powers over captive terrorists in the military appropriations act of 2012, that legislation declared that “[n]othing in this section is intended to . . . expand the authority of the President or the scope of the Authorization for Use of Military Force [of September 2001].” If the administration wishes to escalate the fight against terrorists in Yemen, it should return to Congress for express approval.

Obama has an option. He has avoided Bush-era claims that he has the unilateral power as commander in chief to open up new fronts in an endless war against terrorism, independently of Congress. As a constitutional lawyer, he recognizes the weakness of such claims. As a politician he recognizes that they would profoundly alienate his base just when he needs it.

But unless Obama is prepared to cross this particular Rubicon, he should reject Petraeus’s proposal. The president should not try to sleep-walk the United States into a permanent state of war by pretending that Congress has given him authority that Bush clearly failed to obtain at the height of the panic after Sept. 11.