The Department of Justice, including the United States Marshals Service, is in the exective branch, not the judicial branch.

I believe that form is on the U.S. Marshals website -- and many others -- because in certain cases it is the Marshals' responsibility to submit it to the prosecutor. We're still talking about federal trials, though I suppose you could argue that we should have said "executive" since it's the prosecutors' job to file the paperwork. Either way, this form does not apply to legislative cases.