After five years, you'll be fully 'vested' in the company pension plan. [=you will have earned the right to get a full pension when you retire]
Congress is 'vested' with the power to declare war. = The power to declare war is 'vested' in Congress.
She has a 'vested interest' in seeing the business sold, as she'll make a profit from the sale.
(..) Okay, drop him ! Here, hold this. Go! Get out! Listen, no matter what happens, you stay under these vests. You got it? - Yeah. Chopper is coming in! - It's him. Stay down! (..)1991 Terminator 2: Judgment Day