What did he want her to sign?
What was Emily blunt forced to sign?
shareIt was a form to say that they did everything by the book (which they didn't). Because as mentioned earlier the CIA needs another government agency (i.e. The Feds) to be involved in any activity the conduct in the USA. So by signing she is basically saying on behalf of her agency that they didn't do anything wrong.
shareI got to say - If I were her, I wouldn't have any trouble signing the document...
She doesn`t quite chop his head off. She makes a Pez dispenser out of him.
Her signing off was, literally, the only thing they needed from her. Her signature made the op above board, w/o it, the whole thing would end up before a congressional oversight committee.
shareTo say it was a legal operation. It's obviously these guys were basically mercs. US clearly knew about them, but there can be a lot of political unrest and issues from the public/officials that don't know about operations if we just start going and doing a bunch of assassinations and killings in the US.
If they had just gone to Mexico, they wouldn't have needed Kate or anyone from the FBI (US Federal Government). However, because the tunnel led into Arizona, that's why they had to go recruit the feds.