As a quick search didn't turn up a clear result on this: did the UNSC or the UNGA (in this order of authority) give any authorizations or make any recommendations on the use of force against ISIS? And if they were not that explicit, what's the strongest thing they said/recommended be done about it?
N.B., it's easy to find UN condemnations of ISIS attacks, e.g. there's one by the UNSC as late as 20 December, 2022.
The members of the Security Council reiterated that any acts of terrorism are criminal and unjustifiable, regardless of their motivation, wherever, whenever and by whomsoever committed. They reaffirmed the need for all States to combat by all means, in accordance with the Charter of the United Nations and other obligations under international law, including international human rights law, international refugee law and international humanitarian law, threats to international peace and security caused by terrorist acts.
The members of the Security Council reaffirmed their support for Iraq’s security and the continued fight against terrorism, including against ISIL/Da’esh.
Anything other than "ISIS = very bad, we support Iraqi security and combating terrorism everywhere in accordance with international law" from the UN though?