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They may be awarded rights to distribute a Watchmen film, but not the one Warner Bros. just made; at least, not as if it were their own. If you wrote a Watchmen expanded universe novel without permission, for example, you could be sued and not allowed to release it, but DC Comics couldn't then take and it release it as their own.
Anyway, hopefully all this is probably going to mean is that Fox will get a cut of the money. And that a lawyer at WB is probably going to lose their job, if they haven't already.