warning shot in the air DURING a crime in progress not just for fun, is justifiable.
Justifiable or not, it's a bad idea to shoot in the air. It's reckless. I have used a warning shot two times, once against a dog, and it did turn him. Once against a man, and it did turn him. BOTH shots were into the soft ground. If you're in a asphalt parking lot then obviously it would be no better than shooting in the air.
Warning shots are generally a bad idea, I know this, but I really did not want to shoot him unless he forced me too!
I had already drawn to low ready and he thought about it for 2 seconds and then advanced towards me! I put one in the ground and took a couple steps back, I had time to shoot him if I needed. At the shot he decided to break off the attack (thank God!)
It may be against the law to fire warning shots, but can be shown to be a prudent decision if the circumstances are right.