Who or what gives Japan the right to dump nuclear waste into the ocean?

How can they just up and decide to do this? Isn’t it a violation of something? Can’t any agency stop them? It’s just one ocean and it doesn’t belong to anyone, even though there are “rights” given to various countries. How long before we’re unable to use our beautiful beaches for swimming? or before mutated marine life is created? or before we’re no longer able to eat products from the ocean?

“Last week, the operator of the tsunami-devastated nuclear power plant in Fukushima, Japan, began releasing into the Pacific Ocean water that had been used to cool the facility’s reactors.”