President Donald Trump’s decision to bomb Syria on Friday night has (once again) raised an important question: Does the American president have the legal right to order a military strike on another country without the consent of Congress?

The simple answer is no, as Congress is charged with officially declaring war under the US Constitution. But it’s not that simple. For the past several decades, and especially after the 9/11 attacks, Congress has consistently failed to check executive power when it comes to authorizing the use of military force. As a result, the perception of what’s permissible and what isn’t has drifted.

To find out what the law actually says, I reached out to Stephen Vladeck, a constitutional lawyer at the University of Texas. The recent strikes in Syria, he told me, are almost certainly unconstitutional, but there’s now a precedent for them, which means the institution responsible for this crisis — Congress — is the only one that can remedy it.

Our full conversation, lightly edited for clarity, follows.

Sean Illing

As a matter of US law, was the latest American military strike on Syria legal?

Stephen Vladeck

Almost certainly not. To be legal, the strike would have to be authorized either by some act of Congress or by the president’s own powers under Article II of the Constitution. And neither of those conditions appears to have been met here.

Sean Illing

What does Article II say, and why doesn’t it apply here?

Stephen Vladeck

Article II doesn’t say that much; it’s actually quite cryptic in the powers it grants to the president. But two of the powers are important here. The first is what’s called “executive power” (and there’s legitimate debate about whether executive power includes the ability to make war), and the second is the power that makes the president commander in chief of the armed forces.

Since World War II, presidents of both parties have pointed to one or both of those provisions as giving them unilateral power to use military force even when Congress has not authorized it.

Sean Illing

Okay, but under what conditions does a plausible reading of Article II give the president such power?

Stephen Vladeck

Well, that’s the million-dollar question. The only condition the Supreme Court has ever expressly endorsed is to “repel sudden attacks,” which basically means the president doesn’t have to wait for congressional authorization to respond militarily to an attack against us. And I think there’s widespread agreement that, at minimum, the Constitution gives the president that kind of defensive war power.

Sean Illing

That seems reasonable enough, but I don’t see any way to argue that the latest strike on Syria was “self-defense,” since there was no immediate threat to American security.

Stephen Vladeck

Exactly. And indeed we haven’t heard the term “self-defense” from the Trump administration. The term they’ve used instead is that the use of force here was “in our national interest.”

Sean Illing

I think most people accept that the president should have the power to respond to an attack, but in this case, the president is using military force to defend international norms against the use of chemical weapons. Is there any reading of Article II that suggests this constitutes “self-defense”?

Stephen Vladeck

It’s an interesting question whether that “ought” to constitute self-defense, but I can tell you that it certainly never has. And if we expanded Article II to allow the president to use force without Congress any time it furthered some international norm, that would open up a whole host of problems down the road.

Sean Illing

The Trump administration might also claim that the 2001 authorization for use of military force (AUMF), which was passed by Congress after 9/11 and allowed the president to use military force against virtually anyone associated with 9/11, gives the president the power to do what he did in Syria. This is certainly something the Obama administration often invoked in its strikes against suspected terrorists around the world.

Stephen Vladeck

The 2001 AUMF is very specific about who it authorizes the use of force against, and it authorizes uses of force against terrorist organizations responsible for or connected to the 9/11 attacks.

The uses of force we’ve engaged in Syria have largely been against ISIS on the theory that ISIS is sufficiently connected to al-Qaeda that it falls within the purview of that 2001 statute, but there’s no real argument that Assad was in any way connected to the 9/11 attacks, so I see no reason to believe that the AUMF applies.

Sean Illing

So we’re now in a situation in which consecutive presidents are unconstitutionally engaging in acts of war without congressional approval, and it continues because Congress lacks the institutional will to do its job — is that right?

Stephen Vladeck

That’s perfectly said. It may be that for each of these uses of force, Congress is acquiescing because they’re satisfied with the practical results. But from a separation of powers perspective, that’s very dangerous. Congress has a vital role to play in the operation of our government, and it’s not playing it.

Sean Illing

We seem to be in something like a constitutional crisis in terms of how we’ve allowed executive power to expand on this front.

Stephen Vladek

“Crisis” is a strong word. A true crisis would be if Congress actually tried to assert itself and was unable to do so. I think we’re witnessing the effects of a long-term drift in how we understand the war powers of the executive. We’ve come to accept the general unilateral authority of the president to use military force, and that is definitely problematic.

Sean Illing

So where does this leave us? Congress has allowed this precedent to take root, and now it seems the only remedy is for the very institution responsible for this to finally assert itself and exercise its constitutional authority.

Stephen Vladeck

The short answer is that we really need a Congress that cares more about its institutional relationship to the president than it does about the partisan politics of the moment. And I think both parties have been guilty of losing sight of that when they’ve been in power. But I hope we can all agree that we’re better served when every branch of the government plays its role in making these sorts of life-and-death decisions.