Afghanistan’s Taliban govt does hold Afghanistan’s seat in the UN. That govt has failed to pay UN dues and thus the “credentials committee” has removed its voting privilege in the General Assembly.
But . . . it does hold that seat. The previous govt has made no effort to claim the Afghanistan seat. The Taliban govt is the presumed seat holder.
Not sure how much more legal a govt can get. The headline makes no sense. Venezuela’s Maduro govt holds the Venezuela UN seat.
If the UN seat defines “legal” then there is no need to claim anyone is “legalizing” anywhere.