A U.S. drone strike in Iraq on early Friday killed Maj. Gen. Qasem Soleimani, head of Iran’s Quds Force. As Iran vowed retaliation that day, the Pentagon announced it would deploy 3,500 more U.S. troops to the Middle East.

All that sounds a lot like “the introduction of United States Armed Forces into hostilities, or into situations where imminent involvement in hostilities is clearly indicated by the circumstances.” According to the 1973 War Powers Resolution, that requires congressional authorization. How do current events fit into that framework? Let’s examine that step by step.

What does the War Powers Resolution require?

In the resolution, presidents are empowered to use force when there is a declaration of war; a specific statutory authorization; or “a national emergency created by attack upon the United States, its territories or possessions, or its armed forces.” The first hasn’t occurred. But the other two might be pressed into service.

Congress passed the 2001 Authorization for the Use of Military Force to respond to the 9/11 terrorist attacks, most obviously to fight al-Qaeda and the Taliban. Over time, though, it has become the go-to language for executive branch lawyers, who have stretched it to reach far beyond those foes. The 2001 authorization has been used to attack the Islamic State and even various terrorist groups operating in Africa. Still, it can’t plausibly reach to Iran — a sovereign nation whose government was not involved in the 9/11 attacks (and whose Shiite leaders are considered apostates by al-Qaeda’s Sunni devotees).

What about the law authorizing war with Iraq, passed in October 2002 and also still on the books? Soleimani was deeply involved in organizing militias that attacked U.S. troops and killed Iraqi civilians in the aftermath of the 2003 invasion. Even so, the 2002 Authorization for the Use of Military Force specifies that its purpose is to “defend the national security of the United States against the continuing threat posed by Iraq,” not Iran, and to “enforce all relevant United Nations Security Council resolutions regarding Iraq,” which are now moot. It predates the government of Iraq, which has denounced the Suleimani strike as violating the more recent deal the United States cut to allow its troops to operate there. Brian Egan and Tess Bridgeman at Just Security therefore argue that “we do not believe that there is any existing congressional authorization to use force against Iran.”

What about the third option, in which presidents are empowered to use force in a “national emergency created by attack upon the United States, its territories or possessions, or its armed forces?” The War Powers Resolution contemplates that the president might (as discussed at the Constitutional Convention) need to “repel sudden attacks.” As I have written here before (about Syria, the Islamic State and Syria again), presidents using force without resolution authorization have often invoked self-defense. That includes President Jimmy Carter’s failed 1980 attempt to rescue American hostages in Iran and President Bill Clinton’s 1998 missile strikes retaliating against al-Qaeda’s U.S. Embassy bombings in Africa. Even President George H.W. Bush explained his invasion of Panama as a response to Gen. Manuel Antonio Noriega’s “reckless threats and attacks upon Americans in Panama [that] created an imminent danger to the 35,000 American citizens” there. President Ronald Reagan had justified invading Grenada in 1983 along similar lines.

The Trump administration has indeed argued that it launched the Soleimani strike as “decisive defensive action,” in the Pentagon’s words, to preempt future attacks against the United States. “We took action last night to stop a war,” President Trump said in Florida on Friday, saying Soleimani was “caught in the act” of “plotting imminent and sinister attacks on American diplomats and military personnel.”

The Pentagon has said it does not know of any “imminent” attacks. Still, Soleimani was involved in many efforts to harm Americans, and this reasoning might plausibly cover a direct retaliatory strike. It would not seem to extend to a more sustained conflict.

There’s a long history of presidents using force unilaterally

Does the president even need to worry about the War Powers Resolution? After all, Article II of the Constitution makes the president commander in chief of the armed forces.

It was not obvious to the framers of the Constitution that the title gave the president independent authority on when to act. As late as the 1950s, Congress debated whether the president had sole authority even to move troops from one place to another.

But over time, presidents’ unilateral actions have created practical precedents — and executive branch lawyers have built a latticework of legal justification to support those actions. The Justice Department’s Office of Legal Counsel, for instance, holds that Article II gives the president the power to use force when the president believes there is an important “national interest” in doing so, and when the force does not constitute war. War, the office argues, means “prolonged and substantial military engagements, typically involving exposure of U.S. military personnel to significant risk over a substantial period.” This rationale allowed the Obama administration to claim that 2011 military operations in Libya did not count as war or even “hostilities” under the War Powers Resolution. The Trump administration took the same route to justify its 2017 and 2018 airstrikes against Syria over its use of chemical weapons.

Further, as former Office of Legal Counsel chief Jack Goldsmith points out, the office has issued additional opinions that specifically underwrite presidential military action against terrorism. These claim that “the Constitution vests the President with the power to strike terrorist groups or organizations that cannot be demonstrably linked to the September 11 incidents, but that, nonetheless, pose a similar threat to the security of the United States and the lives of its people, whether at home or overseas.” This may be one reason Trump called Soleimani “the number one terrorist anywhere in the world.”

The president will probably be perfectly happy to rest on these self-grown legal precedents, which leaves the ball in Congress’s court. Past efforts to assert congressional prerogatives here have failed — perhaps because the status quo allows legislators to complain about presidential action without taking responsibility. However, Sen. Tim Kaine (D-Va.) has already filed a measure seeking to activate the War Powers Resolution; others have called for a new Authorization for the Use of Military Force to supersede the 2001 and 2002 editions. Last year, bipartisan, though not veto-proof, coalitions pushed back against Trump’s Middle East policies, voting to cut off support for Saudi air attacks on Yemen and to block arms sales in the region.

Few outside Iran will mourn Soleimani’s death. But the wider consequences of that death are a matter for deliberation — something for which Congress is built. Good policy is as crucial as clear legality. In other words, is war with Iran a good idea? That is not the president’s call alone.