The Marshall Islands has pulled up the US government over its interpretation of treaty law in a continuing David and Goliath legal battle over nuclear disarmament.
The two sides have been submitting their briefs for the appeal by the Marshall Islands against a US federal judge's decision to throw out the case.
The Marshall Islands says the US government lawyers have broadly misstated the law surrounding treaty disputes as it pushes ahead with its so-called Nuclear Zero lawsuit.
The country, which was used as a testing ground for the US' nuclear programme in the forties and fifties, launched action last year to get the world's nuclear powers to honour their promise to disarm under the Nuclear Non Proliferation Treaty.
But the case against the US was thrown out in February on constitutional grounds.
In its appeal brief the Marshall Islands says the US courts do have the power to oversee disputes over international treaties saying no law elevates the president's authority to make a treaty above the judiciary's power to decide disputes.
It also argued it can bring the suit because the US has violated its treaty negotiations and because of the measurable increased danger it faces.
The government contends even if a foreign state was able to sue in US courts, it can't challenge the president's foreign affairs responsibilities.
The Marshalls' Foreign Minister Tony de Brum earlier said the Marshall Islands would use every legal avenue to make sure the lawsuit is won in his lifetime.
The Court of Appeals for the Ninth Circuit will now appoint a three-judge panel to consider the briefs.