Keith Harbaugh wrote two questions, the first of which is:

1. Does anyone know the legal status of such a request? (Under French, UK, US, or UN law.)

As people have discussed at the Secret Blogging Seminar http://sbseminar.wordpress.com/2010/02/09/grothendiecks-letter/ (that's the same link that appeared earlier in this thread), Grothendieck doesn't seem to be relying on the legal system. Nevertheless, since you ask: In every signatory to the Berne Convention (which is most of the world, including the wealthy countries where almost all mathematics is produced now), anything whatsoever is automatically copyright once in a "fixed form", for at least 50 years after the death of an individual author, unless there is some special rule that says otherwise. If Grothendieck has ever given someone permission to publish something, he probably cannot withdraw it; otherwise, it is copyright already. But the details (what is fixed?, what is permission?, what is publishing?) can get complicated, which is how intellectual property lawyers make money. If Grothendieck and his heirs aren't going to sue or complain to the police, then there may be ~no~ legal consequences. But there may be fear of such, or else (as Grothendieck writes in his letter) a moral "shame" ("honte"). --Toby [For admin and other information see: http://www.mta.ca/~cat-dist/ ]