British Marines near Gibraltar seized a ship allegedly carrying Iranian oil to Syrian (archived). The Brits are defending their theft as an act of "EU sanctions enforcement" despite Marines capturing a foreign vessel in transit from a nation outside the EU to another nation outside the EU, while the thieves themselves are Brexiting anyways.
Iran responded by summoning their British ambassador to explain that in the international law texts Iran has read, the EU sanctions against Syria are not only illegal and further Iran wouldn't have to recognize the sanctions even if they were "legal" through some twisted confusion of terms.
Thusly Major General Mohsen Rezaee of Iran's Revolutionary guard announced to the world that Iran has a duty to capture a British tanker ship.1
Should Britain actually have any oil tankers. ↩