Trump has extended a waiver on a century-old shipping law, a move that could bring some relief to Hawaii's energy costs but which critics say barely moves the needle.

• The waiver lets shippers use foreign tankers instead of American-built ones to move fuel, diesel, and fertilizer, with the goal of easing energy prices.
• Hawaii has received several shipments under the waiver, including a propane shipment that mattered a lot since no Jones Act ship can even carry propane.
• The Hawaii shipping industry backs keeping the original law in place, arguing it protects American shipbuilding jobs and national security.
• Critics argue the law still unfairly drives up costs for Hawaii, which ships in most of its goods, and say the waiver's savings have not offset other price increases.
• A Hawaii-based think tank plans to release a report estimating how much prices would have risen without the waiver, aiming to build the case for reforming the law.

Outlook: The debate over permanently changing the law is likely to keep going as more data comes in on how much the waiver actually saved consumers.