Mark Mazzetti, Adam Goldman and Michael Schmidt report:

The end came quickly for one of the costliest covert action programs in the history of the C.I.A.

During a White House briefing early last month, the C.I.A. director, Mike Pompeo, recommended to President Trump that he shut down a four-year-old effort to arm and train Syrian rebels. The president swiftly ended the program.

The rebel army was by then a shell, hollowed out by more than a year of bombing by Russian planes and confined to ever-shrinking patches of Syria that government troops had not reconquered. Critics in Congress had complained for years about the costs — more than $1 billion over the life of the program — and reports that some of the C.I.A.-supplied weapons had ended up in the hands of a rebel group tied to Al Qaeda further sapped political support for the program.

While critics of Mr. Trump have argued that he ended the program to curry favor with President Vladimir V. Putin of Russia, there were in fact dim views of the effort in both the Trump and Obama White Houses — a rare confluence of opinion on national security policy.

Now that the program has ceased, it’s worth a brief reminder that it raised–and continues to raise–at least three important legal questions.

First, once then-Secretary of Defense Hagel (in 2013) and several Senators (in 2014) publicly acknowledged the program, what was the justification for it remaining “covert,” in the sense that U.S. officials continued to be precluded from discussing it publicly or even acknowledging its existence?  As Jack Goldsmith and I discussed here, there was no obvious reason why such secrecy and nonacknowledgement had to have, or should have, persisted.  This question is even more acute today, now that President Trump acknowledged the program in a tweet.

Second, did the provision of arms to the rebels breach the prohibition on “use of force” in Article 2(4) of the U.N. Charter, and other, customary rules of international law?  As Ashley Deeks and Michael Schmitt explained (see also Mike with Ryan Goodman here), the answer is almost certainly “yes.”  If the Obama Administration was internally relying upon a legal argument for why the aid did not violate international law, it would be a good idea for someone to publicly present that argument now, after-the-fact, so that the precedent established by the program can be better understood by other nations, the public, and future Presidents–particularly if the legal rationale depended upon limits or conditions that might circumscribe the potential breadth of that precedent.

Third, if the program did breach the Charter and other international law constraints, what was the authority under U.S. law for doing so–particularly since the Charter is not only an international law instrument but also a treaty that is the supreme domestic law of the land?  Has Congress actually authorized the President to breach certain U.S. treaty obligations, as long as he does so by way of covert action?  I discuss this and related questions in some detail in this post, written in response to Charlie Savage’s account of the legal questions surrounding the bin Laden operation in Pakistan.

Photo: A member of the Free Syrian Army patrols in the border town of Jarablus, August 31, 2016 – Defne Karadeniz/Getty Images