Australia was a founding signatory to the High Seas Treaty in 2023, with the federal government promising to ratify its commitment "as quickly as possible".
The treaty required approval by 60 nations for it to become law and that target was met on Friday, when Morocco became the 60th, meaning the law will take effect in January.
Greenpeace Australia Pacific campaigner Elle Lawless said it was disappointing Australia wasn't yet among the signatories, despite being one of the first countries to sign the treaty at the UN General Assembly in 2023.
"Today is a global win but a domestic disappointment," Ms Lawless said.
The treaty lays the foundations to safeguard 30 per cent of the world's oceans by 2030 in marine sanctuaries, helping preserve threatened species and support fish stocks.
The Climate Change Department had announced that federal legislation was needed before the treaty could be ratified.
The treaty was tabled in parliament in June 2024 and was to be considered by the Joint Standing Committee on Treaties before the legislation was introduced.
However its current status is unclear.
Greenpeace is calling on Australia to rapidly ratify the treaty and propose ocean sanctuaries in the waters between Australia and New Zealand.
The South Tasman Sea and Lord Howe Rise are of critical importance for protection and are identified by the UN as areas of special biological significance.
The treaty is a critical tool "that will give the ocean a shot at survival by allowing the creation of high seas ocean sanctuaries where marine life can rest, recover and thrive", Ms Lawless said.
"The ocean needs a life buoy and the Australian government is holding one in the treaty," she said.
Less than one per cent of the high seas are fully or highly protected.
The treaty is crucial to expanding protection, establishing sanctuaries that help mitigate the climate crisis and safeguarding food security for the billions who depend on ocean resources.
"It's not too late. Australia hasn't missed the boat but had better start swimming if it's to catch up," Ms Lawless said.
