Jarts were not banned by law, the sale was banned by the Consumer Product Safety Agency. From what I can see there have been three deaths from Jarts. Originally the ban, merely banned them as being labeled as children's toys. In 1988 they were not allowed to be sold. Manufacturers have skirted the law since, but selling components separately. I did find one incident in Elkhart, IN in 1997 where a 7 year old had his skull pierced by a Lawn Dart. No word on whether he survived or not.
This ban, merely bans the retail sale of Lawn Darts. If I have Jarts in my possession, men with guns are not going to come to my house and steal my legally purchased possession.