What intervention rights does a coastal State have where a ship on the high seas has suffered a casualty and poses a risk of pollution to the State’s waters?

Under a convention widely known as the Intervention Convention 1969, the government of any State that is threatened by pollution may take measures to prevent, mitigate or eliminate any grave and imminent danger of pollution. 

The government must consult, if possible, with other affected governments, including that of the ship’s flag State, the owners of the ship and cargo, if known. Measures taken must be reasonably necessary for the purpose, and compensation is payable if damage is caused by excessive measures.