Tensions between the United States and Iran are flaring—and possibly headed toward war if left unchecked.

Attacks against Japanese and Norwegian tankers in the Straits of Hormuz, which the United States has blamed Iran for despite skepticism from European allies, coupled with Iran’s announcement that it would violate the 2015 multinational nuclear deal that the Trump administration withdrew the United States from in 2018 and President Trump’s move to deploy an additional 1,000 troops to the Middle East, have created sky-high tensions between the two countries.

Should the Trump administration take military action against Iran, officials have suggested that the president already has authorization from Congress to attack Iran, which has drawn intense skepticism and outrage from members of Congress and legal experts.

“We always have the authorization to defend American interests,” said Secretary of State Mike Pompeo on CBS’ Face the Nation on Sunday, when asked whether the administration had the legal authorization to strike Iran.

Lawmakers have said that the administration in private has stated it does not need their backing, and it has floated using the same legal authority that the Bush administration used after September 11, 2001, in Afghanistan, despite the fact that there is no evidence that Iran was involved in the terrorist attacks.

Rep. Elissa Slotkin (D-Mich.), a former CIA analyst, said on June 13 that Sec. Pompeo presented to members on “how the 2001 AUMF [Authorization to Use Military Force] might authorize war on Iran.” Rep. Ruben Gallego (D-Ariz.) on May 21, referring to the Pompeo briefing, also confirmed that the administration felt it could attack Iran without authorization: “What I heard in there makes it clear that this administration feels that they do not have to come back and talk to Congress in regards to any action they do in Iran.”

(The State Department did not return a request for comment from Fortune on whether it thought the 2001 authorization applied to Iran; Pompeo did not answer the question before the Senate Foreign Relations Committee, saying he would rather “leave that to lawyers.”)

Pompeo and Trump administration officials have repeatedly said that they do not want a war with Iran. Nevertheless, Pompeo said there is “no doubt” a connection between Iran and al-Qaeda, despite doubts from experts who analyzed al-Qaeda documents that there have been close ties, and no evidence that Iran and al-Qaeda cooperated in terror attacks.

Legal experts and members of Congress from both parties said that the 2001 authorization did not apply.

Heather Brandon-Smith, legislative director for militarism and human rights at the Friends Committee on National Legislation and an adjunct professor at Georgetown University Law Center, told Fortune that there was “definitely not” a provision to use force against Iran in the authorization.

“That is quite a stretch and it’s something we’ve never seen before. It’s certainly not what members of Congress intended when they authorized the president to go after those who attacked the U.S. on 9/11 and those who harbored them,” she said.

“The 2001 AUMF does not authorize the use of force against Iran. Iran was not implicated in the 9/11 attacks, Iranian forces are not al Qa’ida or the Taliban or their associated forces, nor are they a ‘successor’ to any of those forces,” wrote Brian Egan, former legal adviser to the State Department, and Tess Bridgeman, former deputy legal adviser to the National Security Council, in the legal blog Just Security.

Members of Congress have also said that the 2001 authorization does not apply to Iran. Rep. Mac Thornberry (R-Texas), ranking member on the House Armed Services Committee, said on June 13 that he did not think that the authorization applied to the “state of Iran.” Lawmakers, including House Speaker Nancy Pelosi (D-Calif.) and Sen. Rand Paul (R-Ky.), have said that the administration needed to go to Congress to militarily attack Iran.

Further, Pompeo’s comments on CBS about defending “American interests” signaled a legal authority for the president to act militarily as commander in chief under Article II of the U.S. Constitution, which experts doubted applied in the current standoff with Iran.

Steve Vladeck, a professor at the University of Texas School of Law, tweeted, “I must’ve missed the clause in Article II of the U.S. Constitution that authorizes the President to unilaterally use military force in defense of commercial vessels flying foreign flags in international waters…”

Nevertheless, despite recent efforts in the House to repeal the authorization, Brandon-Smith said that Congress bore blame as well for repeatedly balking at repealing it, which has led to a situation where the administration has signaled at an interpretation beyond its intended scope.

“The administration—in three presidents—have interpreted the 2001 AUMF to apply to groups and in places that Congress never intended, and Congress hasn’t done anything to stop that. They’ve continued to appropriate funds for these wars. They’ll criticize what the president does, but they haven’t passed legislation to repeal the 2001 AUMF,” she said. “Instead, Congress has ceded its authority to the executive branch.”

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