As President Trump weighs what actions he wants to take in response to a purported chemical attack in Syria, a debate among lawmakers and congressional scholars has been reignited – what should Congress do about the Authorization for Use of Military Force?

House Minority Leader Nancy Pelosi has said Trump needs a new AUMF from Congress before he can authorize a strike in Syria. And Rep. Jim Jordan, R-Ohio, has called on colleagues to debate bills that grant the president the ability to use military force in general.

Read on for a look at the law and why it’s controversial.

What is AUMF, and why was it created?

AUMF became a public law on Sept. 18, 2001 as a response to the 9/11 terrorist attacks.

The resolution, in part, allows for the president to use “all necessary and appropriate forces against” terrorists who committed or aided in the 9/11 attacks – particularly, Al Qaeda and the Taliban.

Under former Presidents George W. Bush and Barack Obama, AUMF was used to authorize military action in Afghanistan, Djibouti, Ethiopia, Eritrea, Georgia, Iraq, Kenya, the Philippines, Somalia and Yemen.

Another resolution authorizing military force was approved by Congress in 2002, pertaining to Iraq.

Why is it relevant now?

AUMF originally authorized the president to use military force on specific terrorist organizations, but it’s been misused over the years by both Obama and Trump to fight other terrorist groups around the world, Jimmy Gurulé, a Notre Dame law professor, told Fox News.

“It’s pretty obvious just from the text that it was in response to the 9/11 attacks and intended to authorize the president to use force and kill the persons responsible for the terror attacks,” Gurulé, a former assistant attorney general, said. “Here we are 16 years after the authorization was passed by Congress.”

As Trump weighs his options in Syria, lawmakers, such as Sen. Chris Murphy, D-Conn., have called on the president to seek congressional authorization before any military action, such as an airstrike.

But House Speaker Paul Ryan said Trump already has broad authority to attack Syria, saying, "The existing AUMF gives him the authority he needs to do what he may or may not do."

Rep. Justin Amash, R-Mich., disagreed with Ryan's assessment on Twitter.

An error occurred while retrieving the Tweet. It might have been deleted.

Multiple lawmakers also expressed desire to review the broad war authority resolution after the deadly Niger ambush, which left questions as to why U.S. troops are in the African country.

“For 16 years, Congress has remained largely silent on this issue, allowing administrations to go to war anywhere, anytime,” Sen. Tim Kaine, D-Va., said in 2017. “A new AUMF is not only legally necessary, it would also send an important message of resolve to the American public and our troops that we stand behind them in their mission.”

Who is to blame for its misuse?

Although multiple presidents have used AUMF for unintended purposes, both the executive and legislative branches are to blame, Gurulé said.

“There have been repeated efforts to get Congress to adopt a new resolution focused on ISIS, but for many reasons Congress can’t come to an agreement on what the scope of the new AUMF should be,” he said, citing arguments over the type of force, temporal limitations and geographical boundaries.

The House Appropriations Committee voted to strike the 2001 AUMF in June 2017, but the repeal was eventually removed from the defense appropriations bill later that month.

Paul’s bill to sunset the AUMFs was scuttled in September 2017.