By international agreement, obviously. There are tons of international agreements to regulate all sorts of things. It's generally a pretty good way to prevent a race to the bottom. Or in this case, a potential race to the end of the world.
There are international agreements on tons of things that work the same way.
Which would be either very difficult or very ironical, given that realizing that humanity is a threat to humanity precedes that.
Or, if things go well, ending a long very bad chapter.