A group of senators are proposing a new Authorization for the Use of Military Force (AUMF) to replace the existing one. This would clarify that force is authorized against various militant groups, including ISIS, al-Qaeda, and the Taliban, but would not authorize any attacks on any nations, including Syria.
This is seen as an effort to make it more clear what Congress intends to authorize, as the 2001 AUMF has been used by all subsequent presidents as a virtual catch-all for launching new wars without a Congressional debate.
The new AUMF is backed by senators from both parties, including Sens. Bob Corker (R-TN) and Tim Kaine (D-VA).
The new AUMF does not try to set an end-date for war, but would seek a Congressional review every four years. This too is something novel, as the past AUMF has been treated as essentially permanent war against various factions.
Previous suggestions of a revised AUMF have tended to be opposed by presidents, who see them as necessarily limited their power. The Trump Administration has long expressed opposition to a AUMF with any limits.
The Obama Administration felt much the same way, initially bragging their proposed AUMF was even vaguer than the first one. When Congress tried to revise this, the administration quickly turned on the proposal as a threat to national security.