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.
(..) - So? - So that's against the rules and you can't sit with us. Whatever. Those rules aren't real. They were real that day I wore a vest. - Because that vest was disgusting. - You can't sit with us! These sweatpants are all that fits me right now. Fine. (..)2004 Mean Girls