slap (one's) wrist
To issue one with a very mild, inconsequential punishment or warning. The CEO ripped off millions of people, and they're just slapping his wrist instead of throwing him in jail where he belongs. Of course the country going to keep developing nuclear weapons if all we do is slap their wrists for it.
slap someone’s wrist
and slap someone on the wrist tv. to administer a minor reprimand. The courts only slap them on the wrist and send them back out on the streets.