At the narrow passage where a third of the world's seaborne oil flows each day, Iran has drawn a new line — one measured not in naval guns but in financial consequence. Security chief Mohsen Rezaei announced that Tehran will designate a restricted maritime zone around the Strait of Hormuz, threatening to place any vessel that enters on Iran's sanctions list. The declaration transforms a long-contested waterway into a potential instrument of economic pressure, raising questions that trading nations from Tokyo to Brussels cannot afford to leave unanswered.