Sam puts the car back in gear, watching the road. "You are not to talk unless spoken to, unless you are giving your safeword. You will be allowed to call 'yellow' to slow down, but the punishment will not stop until I'm finished unless you use your safeword." Even in punishment, Castiel could stop everything.

"I'm going to warn you now. You're going to be collared for the immediate future." He glances over at Castiel. "If the tattoo and the device isn't enough show of my ownership for you, then I am perfectly happy to be more clear about it."

The fact that they probably wouldn't leave the bunker much in the next few days doesn't mean that the collar won't be punishment in and of itself. After all, Dean and Kevin knew what it meant.