DULUTH — A Duluth head shop was devoid of customers as a city ordinance regulating synthetic drugs kicked in.

Potential buyers at the Last Place on Earth were greeted Thursday with a sign on the door saying the shop wasn’t selling any so-called “incense” products. Callers to the store were told that the ban was temporary and that they might have products available by early next week.

Owner Jim Carlson said he’s awaiting a court decision that he hopes will allow him to sell synthetics despite the city ordinance requiring him to have a license. A federal magistrate judge has scheduled a hearing on his motion today.

Carlson’s attorney, Randall Tigue, said the city’s new requirement that retailers get a license to sell synthetic drugs is unconstitutional.

A 34-year-old woman was arrested on a possible assault charge Wednesday night for allegedly attacking Carlson.

Carlson said he has a restraining order against the woman after she tried breaking into his shop previously. Court records show the woman was charged last month with possessing a synthetic drug and trespassing.

Police Chief Gordon Ramsay said that with the clientele that visit Carlson’s store, it’s surprising that similar incidents don’t happen more often.