From MSNBC:

If the court agrees to hear the case, it would cast a shadow over similar bans in seven states. But declining to take it up would boost efforts to impose such bans elsewhere, at a time of renewed interest in gun regulation after recent mass shootings.

Gun rights advocates are challenging a 2013 law passed in Highland Park, Illinois, that bans the sale, purchase, or possession of semi-automatic weapons that can hold more than 10 rounds in a single ammunition clip or magazine. In passing the law, city officials cited the 2012 shootings at Sandy Hook Elementary School in Connecticut and a movie theater in Aurora, Colorado.