stroke of the pen

with a/the stroke of the pen — одним росчерком пера
Also at the stroke of the/a pen

If someone in authority does something with a stroke of the pen, they sign an official document to make a decision with important and serious results. Used for emphasizing that something important is done by the simple act of signing a document.

Example 1: With the stroke of a pen, the chairman had signed away the company. (MM)
Example 2: He had the power to order troops home with a stroke of his pen. (LDOCE)