The Honolulu County Council approved the ban late last month and Honolulu Mayor Peter Carlisle, who is also the county executive, initially held back his support, saying he wanted to collect more public input due to enforcement and cost concerns.

But when he signed the ban on Thursday, Carlisle was fully committed, especially since retailers were given three years to comply.

“This is groundbreaking. By signing this environmentally friendly bill, Honolulu joined our neighbor island counties,” Carlisle said. “Hawaii has become the only state in the United States where every county has plastic bag legislation.”