Sen. Rand Paul is taking  a stand for Congress’ constitutional responsibility to debate and authorize U.S. wars:
A single senator vowed Monday night to delay the Senate from debating a must-pass, $700 billion defense bill until he is promised a vote to force Congress to pass an authorization for use of military force against extremist groups within six months.
A growing number of lawmakers have been calling for Congress to pass a new AUMF as the war in Afghanistan drags close to its 17th year. But Sen. Rand Paul (R-Ky.) has largely been alone in his quest to force a deadline on Congress, as the chief agitators for a new AUMF, Sens. Tim Kaine (D-Va.) and Jeff Flake (R-Ariz.), have expressed a firm preference for crafting such a measure in the Senate Foreign Relations Committee.
Paul authored an op-ed  explaining why he wanted to end the 2001 and 2002 AUMFs:
Because these authorizations to use military force are inappropriately being used to justify American warfare in 7 different countries. Sunsetting both AUMFs will force a debate on whether we continue the Afghanistan war, the Libya war, the Yemen war, the Syria war, and other interventions.
Of all the current foreign wars the U.S. is involved in, the one in Afghanistan is arguably the only one that can still conceivably be justified under the original 2001 AUMF, and frankly even that seems like a stretch at this point. It can’t possibly apply to U.S. support for the Saudi-led war on Yemen, nor could it provide any authorization for the ongoing war in Iraq and Syria. Each of these other conflicts requires its own proper authorization and debate, if only so that members of Congress are forced to take responsibility for the wars they have tacitly supported until now. The 2002 Iraq war AUMF obviously has no relevance to any conflict in which the U.S. is now engaged. The 2001 AUMF itself was so broad and open-ended that it has since been abused extensively by the Obama and Trump administrations to provide cover for whatever military action they have wanted to take, but the legal arguments they have made to defend their position are risible and shouldn’t be respected.
The issue here is not just that our policy of permanent war needs to be ended. We must also put an end to the executive’s habit of initiating and escalating wars without Congressional approval. This certainly concerns the current illegal wars that the U.S. is waging, but it also matters for future debates over military action. Just a few months ago, President Trump ordered a wholly illegal attack on Syria that Congress never approved, and yet faced no consequences for it. The next time this president or some future one wants to initiate hostilities against another state on his own, Congress must insist on its proper role as the only branch of government that can authorize war.
Paul also wrote a series of tweets giving his reasons for insisting on having a vote. These stood out to me as being especially powerful:
Hypocrites, they pretend concern over our constitutional duty to declare war and then block any vote on ending any of our 7 current wars
— Senator Rand Paul (@RandPaul) September 11, 2017 
I applaud Sen. Paul for speaking out on this. Most members of Congress are content to duck their responsibilities, but he has refused to do that. Most other members evade the clear obligations they have under the Constitution, and in the process they allow the U.S. to be taken into one war after another without any meaningful debate or consideration of the costs and dangers that each new conflict entails. I don’t know if Sen. Paul will be able to shame his colleagues into holding a vote on this question, but he is doing the country an important service by shining a light on Congress’ craven enabling of endless war.
Update: It seems that Paul will get a vote  on his amendment:
Paul’s office announced he would get a vote Wednesday on the Kentucky Republican’s amendment that would repeal the 2001 and 2002 war authorizations after six months, giving Congress time to pass a new Authorization for Use of Military Force for the wars against Al Qaeda, ISIS and the Taliban.
A spokesman for Senate Majority Mitch McConnell did not respond to confirm Paul’s statement, but three Senate aides said a vote was likely on Paul’s amendment.