It's been discussed numerous times. Prohibited but not illegal. I guess better wording would be prohibited but not criminal according to this.
"In 2008, the SEC banned what it called "abusive naked short selling"[2] in the United States, as well as some other jurisdictions, as a method of driving down share prices. Failing to deliver shares is legal under certain circumstances, and naked short selling is not per se illegal.[3][4][5] In the United States, naked short selling is covered by various SEC regulations which prohibit the practice.[6]"
Breath in, breath out, move on. Life's not good,it's great.