Grammar PSA

Grammar PSA

the expression you're looking for is reining in. it is NOT reigning in. it comes from horseback riding.

you REIN IN your horse when you pull on the rein to tell him to slow down.

similarly, you GIVE HIM FREE REIN when you loosen your grip on the reins and let him run as fast as he likes.

that's where the metaphor comes from. you can rein in your evil vizier when he proposes a little too much child murder, or you can give him free rein when you need your enemies obliterated and only underhanded treachery will do. but unless he actually pulls off that nefarious coup he's plotting, the only one reigning here is you.