But it is the first time a Prime Minister has acknowledged the country concerned has explicitly guaranteed to the Government it complied with New Zealand law.
That is the very thing that the United States is not prepared to countenance doing.
Not only that but the US could not countenance a New Zealand Prime Minister making a statutory declaration of US compliance based on his or her assumption a ship complied.
Questioned about the China ship visit, Mr Key told New Zealand reporters in Brunei last night: "They give us that information and I have to sign a declaration that I acknowledge that to be true and correct,.
"American ships would be welcome at any time provided they could comply with the law that's on the books of New Zealand and in the case of these Chinese vessels we know that they meet the criteria of not being nuclear powered or nuclear armed."
The United States policy has long had a policy of neither confirming nor denying nuclear weaponry or capability and China's willingness to vouch for its ships is in stark contrast.
New Zealand's anti-nuclear policy first promoted by the Labour Government in 1984 eventually led to a suspension of the Anzus security alliance that New Zealand had with the United States and Australia.
The suspension was announced at an Asean meeting in Manila in 1986 by former Secretary of State George Shultz.
Mr Key has broached the issue of a visit to New Zealand by a Coastguard vessel with the United States but despite a major improvement in the relationship, it has considered that a step too far too soon.
It has only recently agreed to allow New Zealand ships back into its harbours, and has invited New Zealand to again be a full participant in Rimpac, the largest naval exercise in the world.
Mr Key has been in Brunei to meet leaders of the 10 Asean countries which form a wider group called the East Asia Summit after their second Asean summit of the year.
