The United States said on Tuesday that the American-led airstrikes against the Islamic State — carried out in Syria without seeking the permission of the Syrian government or the United Nations Security Council — were legal because they were done in defense of Iraq…

International law generally prohibits using force on the sovereign territory of another country without its permission or authorization from the United Nations, except as a matter of self-defense. American intelligence agencies have concluded that the Islamic State poses no immediate threat to the United States, though they say that another militant group targeted in the strikes, Khorasan, does pose a threat.

But the letter asserted that Iraq had a valid right of self-defense against the Islamic State — also known as ISIS or ISIL — because the militant group was attacking Iraq from its havens in Syria, and the Syrian government had failed to suppress that threat. Because Iraq asked the United States for assistance in defending itself, the letter asserted, the strikes were legal.

As lawmakers grapple with President Obama’s claim that he already has congressional authorization for airstrikes against the Islamic State, legal specialists are saying that even legislative inaction could create a precedent leaving the executive branch with greater war-making powers…

The Obama legal team’s broad interpretation of the old authorizations has drawn criticism. But several legal specialists said that because Congress was on notice about how the executive branch was interpreting its 2001 and 2002 statutes, any failure to challenge that theory — especially as it enacted other legislation in connection with Islamic State policy — could be interpreted as ratifying it.

“The Supreme Court has said that sometimes, congressional silence means Congress has approved of what the executive has done,” said Barry Friedman, a New York University law professor. “If Congress, for political reasons, is unwilling or unable to speak up and the executive goes forward with its somewhat questionable theory, in the future, courts may well treat Congress’s silence as granting permission.”

The administration remains adamant that Obama has the authority to conduct strikes against ISIS anywhere in the world under the original 2001 law.

A senior administration official Tuesday argued that while the organization is no longer part of Al Qaeda, its past affiliation with the terrorist network means it is covered.

“We don’t believe that Congress would have intended to remove the president’s authority to use force against this group simply because they group had a disagreement with Al Qaeda leadership. So based on that history, based on their longtime connections to Al Qaeda and based on the fact that they continue to be in conflict with the United States and US partners and allies we believe that that the 2001 AUMF would still apply,” the official said.

Ackerman is right that the Obama administration’s reliance on the 2001 AUMF is phony, but he’s wrong to say that Obama has broken with American constitutional traditions. That tradition dictates that the president must give a nod to Congress if he can, but otherwise he is legally free to go to war, subject to vague limits that have never been worked out. That’s not to say that Congress is helpless. It can refuse to fund a war if it objects to it. But the real constraint on the president’s war-making powers is not law, but politics.

It’s worth asking how this came to pass. The founders, who were suspicious of both executive and legislative power, divided the war powers by giving Congress the power to declare war and the executive the authority to lead the troops. The two branches could check each other, keeping us out of unnecessary wars. That’s no longer the case. For while Congress still holds the purse strings, it is hard to cut off funding once the president starts a war.

The answer seems to be that the United States has taken on a global role in a world in which technology makes it possible to attack and be attacked with no warning. To maintain that role, the United States must be ready to use force whenever its interests are threatened, anywhere in the world. Congress is a deliberative body and often can’t be consulted. Even if it can, it has been so taken over by parochial interests that it can’t be depended on to act in the national interest. Aware of its own limitations, Congress has created a standing army and vast intelligence system that operates under the president’s authority, which gives him the practical ability to act on his own. It has tolerated and usually endorsed military actions that the president launched on his own initiative.

It's irresponsible & immoral that instead of debating & voting on war, congressional leaders chose to recess Congress for nearly two months.

— Justin Amash (@justinamash) September 23, 2014

Professor Bruce Ackerman, an excitable liberal at Yale Law School, says that nothing Bush attempted “remotely compares in imperial hubris” with Obama’s “assertion of unilateral war-making authority.” Obama’s administration “has not even published a legal opinion” defending unauthorized war against the Islamic State “because no serious opinion can be written.” Ackerman illustrates William F. Buckley’s axiom that liberals who favor tolerating other views seem amazed that there are other views.

Such as the argument from John Yoo — a Berkeley law professor who served in Bush’s administration — that because presidents are “vested with all of the executive power of the federal government,” they are empowered “to initiate military hostilities to protect the national security,” even if there is no danger of “an imminent attack.” This is extravagant. The Constitution’s text, illuminated by the ratification debates, surely does not empower presidents to wage wars, preventive as well as preemptive, against any nation or other entity whenever he thinks doing so might enhance national security.

Yoo also argues that the 2002 Authorization for Use of Military Force in Iraq authorized force “against the continuing threat posed by Iraq.” So, the Islamic State is now Iraq? Obama insists that he ended the war in Iraq in 2011.

But by leaving town before the president started operations, lawmakers may have done serious harm to their own institution, Sen. Tim Kaine (D-Va.) argued in an interview with The Huffington Post. Not only had they diminished the standing of Congress with respect to the executive branch, they also may have given unintended consent to a Dick Cheney-like vision of presidential war powers.

“[Congress has] sort of allowed the Cheney pre-emptive war doctrine to exist by another name,” Kaine said. “In this instance, they allowed the president to say, ‘ISIL [the Islamic State] is the bad guys, and I can go after them even though there has been testimony that they pose no imminent threat of attack on the United States.’ If the president just gets to do this without Congress, then we will be embracing the Cheney pre-emptive war doctrine, which I think is just brutally wrong.”

[V]oting on the issue would violate the Optimal Preening Principle, which tends to govern these debates.

Killing terrorists, or alleged terrorists, might be popular. But it’s also something the military (and thus, the president) does. Meanwhile, on a good day, Congress votes on legislation. The president might use a new AUMF to do things the public overwhelmingly supports, but that won’t help the embattled congressperson who would have to defend granting the president unlimited warmaking power or defend voting against bombing terrorists because the AUMF wasn’t expansive enough. Instead, by not being forced to take a stance, Obama’s opponents will be able to frame the issue however they want to.

Likewise, when something goes wrong—as it inevitably will—members of Congress won’t want to be linked to it with their votes, and won’t want their votes constraining them from harrumphing about it on camera. Constituents won’t credit them if things go swimmingly anyhow, so they see no upside in sticking their necks out.

The posture that allows for optimal preening is thus to offer qualified support, without taking a vote. From there, you’re free to cheerlead, criticize, even call for a vote that isn’t going to happen, with almost no constraints.

Men in all walks of life change their minds from time to time, and they are often left better off for the shift. But there is something rather slippery about the manner in which this president has managed to transpose himself from a champion of the legislature’s prerogative to an uncompromising advocate for the divine right of kings. At no point have we heard a renunciation of his past position; nor, for that matter, has an explanation of his evolution been forthcoming. Instead, the president has engaged in what, ultimately, is a semantic game, holding theoretically to the “self defense” exception of which he spoke so passionately in 2007, but construing it so broadly as to render it operationally meaningless. The effect of this has been a volte-face, for if, in practice, “self-defense” can be held to justify each and every form of unilateral preemption, there is nothing that a president is not able to do without Congress…

The truth of this matter, as has so often been the case with this administration, is that the law is playing second-fiddle to cold-blooded political expedience. Simply put, President Obama calculated that he would be able to persuade Congress to acquiesce to one measure but not to the other — or, at the very least, that permitting the legislature to weigh in on the latter question would create political problems that his beleaguered party could at present do without. And so, confined by little more than the scope of his ambition, he invented a new set of rules for the day, making it clear to one and all that if getting his way requires him to adopt the legal theories that he rejected so vehemently just six years ago, then so be it; that if achieving his ends requires further entrenching precedents that he was sent into office to smash, then so be it; that if his team must apply to Syria laws regarding Iraq, and to the Islamic State laws that relate to al-Qaeda, then so be it; and that, internationally as well as at home, if Congress insists upon maintaining a mind of its own, then it will just have to be bypassed, too.

But who can challenge the president’s decision to wage war? The answer is almost certainly no one. Certainly not elected officials in Congress. Since 1973, with the passage of the War Powers Resolution, a law intended to restrain the executive branch’s capacity to wage war, there have been multiple attempts by legislators to challenge a president’s legal authority to wage war. None have made a dent in executive authority. In four cases, as the Congressional Research Service noted in 2012, the courts refused to render a decision on the merits, labeling the suits as fundamentally political in nature. Two cases were dismissed for lack of ripeness, and two more were tossed for lack of standing.

As with the delay of the mandate, the recent strikes are probably illegal, and yet no one can mount a challenge. President Obama is unchecked, and uncheckable.

Obama is the only one with the power to stop himself. Indeed, while running for president, that’s exactly what he promised he would do.