United States President Joe Biden campaigned for the White House on a pledge to “end the forever wars in Afghanistan and the Middle East”.
Now, he faces a pressing test of that promise: withdraw US troops from Afghanistan by May 1 as his predecessor Donald Trump agreed with the Taliban, or continue the US and NATO military presence in the country.
By authority of a 2001 US law, known as Authorisation of Use of Military Force (AUMF), the decision is Biden’s to make – even though the US Constitution vests power to declare war in Congress.
Now that open-ended authorisation may be limited as a movement gains momentum for a new AUMF that would narrow the US president’s authority to conduct war in Afghanistan, Iraq and elsewhere.
“Congress should be directly engaged in deciding when and with whom we are at war,” Oona Hathaway, a professor of international law at Yale Law School, told a congressional panel on Tuesday.
Here, Al Jazeera examines the AUMF that first brought the US into Afghanistan, how it has expanded to justify continuing conflict, and what the prospects are for revision or repeal:
In 2001, just three days after the al-Qaeda attacks in New York and Washington, DC, the US Congress passed the AUMF – a declaration of war – giving then-President George W Bush sweeping authority to strike back with armed force.
The congressional action gave the president authority to use “all necessary and appropriate force” against al-Qaeda and those who harboured the attackers, essentially the Taliban. The US invaded Afghanistan on October 7, 2001.
US presidents have interpreted the 2001 AUMF to allow military action against ISIL (ISIS), al-Qaeda, Hezbollah and others in Iraq, Syria, Yemen, Pakistan, Libya and Somalia – drawing concerns from members of Congress, policy analysts and rights groups.
In 2002, Congress passed a second AUMF clearing the way for President Bush’s planned 2003 invasion and occupation of Iraq.
That AUMF gives the US president power to take action to “defend the national security of the United States against the continuing threat posed by Iraq”.
Former President Donald Trump claimed authority under the 2002 AUMF for the 2020 air attack that killed Iranian General Qassem Soleimani at Baghdad airport in Iraq.
That attack angered many US lawmakers who condemned Trump for overstepping his authority.
Biden supports ‘revision’
After a backlash in Congress over a February 25 air raid Biden ordered on a Hezbollah facility in Syria, Biden claimed legal authority for the attack.
But a spokesman signalled the US president would support a revision to the 2001 and 2002 AUMFs.
Attempts to revise or repeal AUMF
US lawmakers in Congress have been debating for years whether and how to repeal or revise the 2001 and 2002 authorisations. There is bipartisan agreement that both AUMFs are outdated, but Republicans and Democrats diverge on details of any replacement authorisation.
Former President Barack Obama in 2015 asked Congress to authorise a three-year limited war against ISIL (ISIS) in Syria and Iraq. The bid failed.
In 2019 and 2020, the House approved a pair of Democratic-backed measures to repeal the 2002 Iraq authorisation and prohibit war with Iran, but both failed to win Republican support in the Senate.
Congress also passed a bill in 2019 that would have ended US military support for the Saudi-Emirati coalition waging war in Yemen, which was justified in part by Obama as part of the US’s war against al-Qaeda. Trump vetoed it.
View in Congress now
A debate has begun anew in Congress, and with a Democrat in the White House, Republicans are showing more interest in curtailing the president’s powers.
“This year marks 20 years since 9/11. It is past time to review and reflect on the decisions made in the aftermath of that dark day,” Republican Representative Michael McCaul said during a hearing of the House Foreign Affairs Committee on Tuesday.
“Wars should not be on autopilot,” McCaul said.
Congress should enact a new war authorisation “scoped to the current terrorist threats to replace the 2001 and 2002 AUMFs that are still on the books”, McCaul said.
In the Senate, Democrat Tim Kaine and Republican Todd Young have introduced legislation that would repeal the 2002 AUMF and an earlier one from 1991. Biden’s air attack in Syria showed “the executive branch, regardless of party, will continue to stretch its war powers”, Kaine said.
It is unclear when the proposed bill would get a Senate vote – and Biden could veto any outcome he disagrees with.