Donald Trump is surely very happy Friday with the coverage noting the contrast between his quick response to a Syrian chemical weapons attack and that of the Obama administration in 2013. The New York Times notes that Trump’s airstrikes “appeared intended to maximize the element of surprise, and contrasted sharply with the Obama administration’s methodical scrutiny of a military response.” Reuters reports, “In the biggest foreign policy decision of his presidency so far, Trump ordered the step his predecessor Barack Obama never took.” But Trump also owes the Obama administration some gratitude for providing the legal cover for carrying out these strikes in the way that he did.

A number of lawmakers are criticizing the president Friday for not seeking authorization from Congress for Thursday night’s strike, as Obama did in 2013. “His failure to seek congressional approval is unlawful,” said Sen. Tim Kaine. “[T]he United States was not attacked. The President needs Congressional authorization for military action as required by the Constitution,” said Sen. Rand Paul.

At this point, it’s the norm, rather than the exception, for the president to order military action without asking Congress first. Still, even when presidents circumvent that check, they’re usually able to make some semblance of a case for the strike being necessary to protect U.S. interests. It’s very hard to make that case this time.

These strikes are similar in some ways to the brief bombing of Libya ordered by Ronald Reagan without congressional authorization in 1986, but those were in response to a terrorist attack in Germany, blamed on Libya, in which two American soldiers were killed. There were no Americans killed in this week’s chemical weapons attack in Idlib. Yes, there are U.S. troops operating in Syria, but there’s not much evidence to suggest that Bashar al-Assad’s chemical weapons program poses a threat to them.

Rather, this was an operation justified on the basis of upholding international norms. Trump made this clear in his speech Thursday night:

There can be no dispute that Syria used banned chemical weapons, violated its obligations under the Chemical Weapons Convention, and ignored the urging of the UN Security Council. Years of previous attempts at changing Assad’s behavior have all failed, and failed very dramatically. As a result, the refugee crisis continues to deepen and the region continues to destabilize, threatening the United States and its allies. Tonight, I call on all civilized nations to join us in seeking to end the slaughter and bloodshed in Syria, and also to end terrorism of all kinds and all types.

But the U.N. Security Council never authorized a military operation to punish Syria’s violation of the convention. With Assad’s ally Russia on the council, this was never going to happen.

Another precedent that’s likely to come up in discussions of this attack is Bill Clinton’s 1999 bombing of Serbia to deter aggression against Kosovo, a humanitarian intervention conducted without authorization from either the Security Council or Congress. But that at least had the authorization of NATO.

Whether the U.N. or NATO’s approval can substitute for congressional authorization is a controversial notion anyway, not that Trump, who has expressed contempt for these bodies, would actually seek it.

This brings us to the Obama administration. Prior to coming to office, the former constitutional law professor argued that the president “does not have power under the Constitution to unilaterally authorize a military attack in a situation that does not involve stopping an actual or imminent threat to the nation.” But once in office, he took a more flexible view.

The 2011 bombing of Libya, initially meant to prevent a feared imminent massacre by Qaddafi’s forces in Benghazi, was authorized by a Security Council resolution and conducted under the auspices of NATO, but as Jack Goldsmith pointed out on Lawfare Thursday night, Obama’s Office of Legal Counsel also argued at the time that the president has the right to act unilaterally in defense of the “national interest,” which in the Libya case was “preserving regional stability and supporting the UNSC’s credibility and effectiveness”—language not all that unlike what Trump used last night.

Obama also set a precedent under which limited, short-duration strikes require a different standard from long-term engagements, which would require congressional authorization under the War Powers Resolution. As Obama’s spokesman Jay Carney put it in 2011, “these constrained and limited operations do not amount to hostilities under the War Powers resolution.”

Of course, as many Democrats are pointing out Friday, when Obama was considering his own strikes to deter Assad’s chemical weapons use in 2013, he did decide to ask Congress for authorization. This happened only after the British Parliament had rejected intervention, meaning the U.S. would have limited international support, and it became clear that U.S. public opinion was steadfastly against the operation. It also seems likely that Obama didn’t really want to intervene in Libya—he hemmed and hawed publicly about whether it was legal—and brought it to Congress knowing it would fail.

But what’s less remembered now is that prior to seeking a congressional vote, the Obama administration argued that it didn’t actually have to. Charlie Savage of the New York Times reported on Sept. 8, 2013:

In recent weeks, Administration lawyers decided that it was within Mr. Obama’s constitutional authority to carry out a strike on Syria as well, even without permission from Congress or the Security Council, because of the “important national interests” of limiting regional instability and of enforcing the norm against using chemical weapons.

Trump has now essentially taken the authority that the Obama White House believed it had, but chose not to use, and run with it.

As less a legal than political matter, it’s also worth considering that the U.S. has already been bombing Syrian territory since 2014. There’s a difference, of course: These strikes are against ISIS and justified—somewhat dubiously—under the 2001 Authorization for the Use of Military Force against terrorists. Sturdy and flexible as that AUMF has been over the years, it would probably be a step too far to apply it to attacking Assad’s military. That said, the Obama administration conducted war in the Middle East, with little involvement of Congress, in a remarkably open-ended way, and reserved for itself seemingly limitless authority to launch limited airstrikes or in-and-out special operations missions in countries where the U.S. was not at war.

Questions of executive power in war are often more a question of political precedent than written law, and the way the previous administration conducted operations in countries including Pakistan, Syria, Libya, Yemen, and Somalia helped normalize the notion that limited airstrikes are not “real” war. Most Americans probably won’t see a massive distinction between bombing one set of bad guys in Syria or another, unless this evolves into something much larger and more dangerous.