You should probably have bothered to read the actual resolution in question before posting because if you had you would`ve seen that the statement you posted is simply not correct.Here is the relevant part of the resolution in question [res#2249]
5.Calls upon Member States that have the capacity to do so to take all necessary measures,
in compliance with international law, in particular with the United Nations Charter...
As you can see this in no way at all gives the us or anyone else carte blanche to come into syria and violate its sovereignty nor does it give anyone the right to occupy syrian territory,to support insurgent/terror groups and to attack syrian military or allied forces.The us presence in syria is
NOT legitimate in any way unlike the russian,iranian and other allied forces that were formally invited into syria by the legitimate government of syria.
In fact the resolution begins with this:
Reaffirming the principles and purposes of the Charter of the United Nations,Reaffirming its respect for the sovereignty, territorial integrity, independence and unity of all States in accordance with purposes and principles of the United Nations Charter
Sadly the us seems rather hellbent on ignoring this particular section.Heres a link to the resolution in question,read it for yourself if you like
https://www.un.org/en/ga/search/view_doc.asp?symbol=S/RES/2249(2015)