The Trump administration will keep the US military in Syria and Iraq indefinitely without new congressional authorization, according to the New York Times, citing State Department and Pentagon officials.
This decision will likely extend to the US' broader fight against terrorism, which is being waged in numerous countries around the world, such as Afghanistan, Yemen, and Somalia.
The last comprehensive congressional authorization to use military force (AUMF) came in 2001 when the legislative body authorized former President George Bush to "use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons, in order to prevent any future acts of international terrorism against the United States by such nations, organizations or persons."
Another congressional AUMF was also passed in 2002, but it only allowed the use of military force in Iraq.
After Bush, the Obama administration used the 2001 AUMF to justify airstrikes against ISIS, and other terrorist groups, arguing that ISIS was al-Qaeda's affiliate in Iraq from 2004 to 2014.
"This is a weak argument," Cornell University Law School professor Jens David Ohlin said in 2014. "Yes, ISIS once had a relationship with al-Qaeda and Osama Bin Laden, but that prior relationship no longer governs. What matters is the current relationship."
U.S. Army Pfc. Rohan Wright, center, a cavalry scout with a personal security detachment with the 4th Brigade Combat Team, 101st Airborne Division, prepares to fire an M320 Grenade Launcher Module (GLM) at the weapons range at Forward Operating Base Thunder in Paktia province, Afghanistan, Oct. 18, 2013. (US Army photo by Sgt. Justin A. Moeller)
Many other legal scholars struck a similar tone.
"Congress is supposed to be declaring war, and the president is supposed to be making war," Jennifer Daskal, a professor at American University and former Justice Department lawyer, told NPR in 2016.
"There appears to be a clear abdication of responsibility on behalf of Congress," Daskal said, adding that it sets a dangerous precedent and could allow future presidents to use the military at his or her own discretion.
Some members of Congress, however, such as Republican Senator Jeff Flake and Democratic Senator Tim Kaine, have introduced new AUMFs over the years to no avail.
More recently, Kaine voiced his concern over what this means for the US military's role in Syria, where it will remain even in territories of the country where ISIS fighters have been cleared.
"I am concerned that the United States will soon find itself lacking domestic or international legal standing for operations in Syria based on official statements that our presence, intended for a narrowly-scoped campaign to fight ISIS, might now be used to pressure the Syrian government, target Iran and its proxies, and engage other entities not covered under the 2001 AUMF," Kaine wrote to US Secretaries Rex Tillerson and James Mattis in December 2017.
"The United States does not seek to fight the government of Syria or Iran or Iranian-supported groups in Iraq or Syria," Mary K. Waters, the assistant secretary of state for legislative affairs, wrote back. "However, the United States will not hesitate to use necessary and proportionate force to defend U.S., coalition, or partner forces engaged in operations to defeat ISIS and degrade Al Qaeda."