Nowhere does it say who can authorize the license, or how that is accomplished.
I went down this rabbit hole in another thread. My thinking is that it is implied by who can publish new versions. Ryan Dancy recently went on record stating that "authorized" was supposed to discriminate between draft and non-draft versions. How I read that is that I am free to release content under the text of 0.1 linked above. Someone could then accept that license I offered to use my content. That person would then hold a valid license that arguably would be an OGL version published by wizards. However as it was considered a draft (not authorized), that person wouldn't be able to use that license to copy 1.0a material.
However someone obtaining a 1.0a license would (likely)be able to copy the material published under the 0.1 license.
Under this interpretation of "authorized", I think it would be common sense that it is the ones entiteled to publishing new license versions that would be the ones responsible for making clear if what they just published is a draft or not? That a version can go from being a draft to becoming considered a "non-draft" version when it is found to be good enough I guess is completely uncontroversial? That something can similarly be declared to go back to "draft" is however more problematic. However if such a thing was possible on a "global" level, I guess it would make sense that it would be only those responsible for declaring it a non-draft that could do this.
However from a legal perspective wizards is seemingly seeking several viable interpretations of how they can remove authorization. Another one is the presence of the term in a contract as opposed to for instance in a press release. In that case it would be the parts entering the contract that agree to "pretend" 1.0(a) is not authorized. As none of the parties gain any extra rights they had before by doing such a "play pretend" I don't see why not anyone could write a contract with such a "no longer authorized" language. However the other way around would as far as I can see not be possible, as that would be claiming new rights the contractors might not be entitled to grant themselves.
However on this second interpretation the lack of authorization would only affect those bound by the new ogl.
A third path they seem to take is to delete the current ogl from their website. This could be a play at words with regard to "wizards can publish new versions", and by no longer "publishing" it that somehow change the state of the version.
I am no lawyer, and I agree to the sentiment that the practical effect of this isn't neccessarily tied to law, but the fact that it is effectively scaring people off due to all the ambiguities this create. But I hope this can help explain how wizards can justify claiming to be in a privileged position to determine "authorization".