The mention below of Pacific states not having joined the Convention Against Torture raised the question of what else they haven't signed up for. So, I did some digging. Below is a map of the members of the International Covenant on Civil and Political Rights, one of the core UN human rights documents which served as the foundation for our own Bill of Rights Act:
(Click the map for a larger version. Source here)
Note the large gap in the South Pacific. Clearly something else our government should be trying to persuade our neighbours about.