New Zealand's security treaty with the United States, ANZUS, did not mention nuclear deterrence and did not require unconditional port access. However, after New Zealand refused entry to USS "Buchanan" in 1985, the United States government suspended its ANZUS obligations to New Zealand, seeing New Zealand's effective rejection of United States Navy vessels as voiding the treaty. The Lange Labour government did not see their stance as incompatible with the treaty and sought a compromise for over two years before passing the Act. Support for the non-nuclear policy was bolstered by the perceived over-reaction of the United States and by the sinking of the Rainbow Warrior by French spies while docked in Auckland. According to some commentators, the legislation was a milestone in New Zealand's development as a nation and seen as an important act of sovereignty, self-determination and cultural identity. New Zealand’s three decade anti-nuclear campaign is the only successful movement of its type in the world which resulted in the nation's nuclear-free zone status being enshrined in legislation.