Regional campaigners against the global arms trade say Pacific Island countries should follow Samoa's lead and ratify a landmark international treaty.

Samoa is the first among Pacific Island countries to ratify the Arms Trade Treaty which seeks to thwart the flow of arms to conflict regions.

Kiribati, Nauru, Palau, Tuvalu and Vanuatu have signed but ratification is needed in order to be bound by the UN agreement's rules.

Samoa's move brings to 40 the number of states which have ratified and 50 are needed before the treaty comes into force.

Ema Tagicakibau of the Pacific Small Arms Action Group says Samoa has shown leadership on the issue.

"Pacific states should really take a leaf from Samoa's example and sign on and ratify it as soon as possible for the good of the region, for our human security and for our development and for our own safety and for the long term peace in the region."

Ms Tagicakibau says the treaty requires ratifying countries to make their own laws around the movement of guns and other arms.