My understanding in the United States is that the federal government can't copyright. I'm not sure how this affects other governments, but the must own the copyright issue shouldn't apply to US government documents.

I'm pretty near certain that is the case. But this is probably more about lawyering than anything else: "Your Honor, to our knowledge the submitter of the document owns the copyright and any infringement is born entirely by them."

It would be a good way to publish something that has no value.