Spanking should be legal. Marks should be legal. Big honkin S&M style 3-week bruises, not so much. But welts that are gone in 24-48 hours sure. Depending on age. Don't do that to a 3-year old.
You have to be able to inflict enough pain to instruct, otherwise, it does nothing. And the older they get, the more pain they can laugh off at you. By the time I was 13, my parents couldn't legally hit me hard enough to make a difference. Result? A lot of years struggling with issues that could have been avoided by 10 seconds with a belt. 10 seconds of pain from a belt, or 10 years of working to overcome the lack of discipline?
Wish they'da hit more and harder. Could be a billionare by now
Also, never hit angry. The lesson is then lost, the child learns nothing benneficial, and you may not stop when you should.
Slap to the face can work too, but that should not be heavy. A slap to the face should be used to correct verbal disobedience, and should be done in mid-sentance. It interrupts the pattern the child is in, and allows fast instruction. And lets face it, a slap doesn't have to hurt to stop someone in their tracks. Think about all the times someone popped you in the chops when you were hitting on them, and how fast you stopped talking. May only be for an instant, but the momentum is broken, and that's the whloe point.
Now a days time outs and grounding are about all you can do. And I can tell you from experience, it don't work as well as one good hard shot across the buttocks with a good old fashioned switch. Especially when you gotta go get the switch yourself.
CJ