A recent Supreme Court decision marks a significant development in New Zealand's legal system becoming progressively more inclusive of tikanga Māori.

The case related to Trans-Tasman Resources' (TTR) application to mine 50 million tonnes of sand a year from the seabed within New Zealand's exclusive economic zone (EEZ). TTR applied for marine consents and marine discharge consents from the Environmental Protection Authority (EPA) under the under the Exclusive Economic Zone and Continental Shelf (Environmental Effects) Act 2012 (EEZ Act).

The Decision Making Committee (DMC) of the EPA granted the consents in 2017 for 35 years but several groups successfully challenged the DMC's decision in the High Court. The High Court's decision was upheld by the Court of Appeal. The Supreme Court has unanimously dismissed TTR's appeal, finding errors in the DMC's decision making process. The Supreme Court has referred TTR's application back to the DMC to reconsider.

The Supreme Court's decision discusses issues relating to the interpretation and application of the EEZ Act. Although the decision being challenged was made under the provisions of the EEZ Act, aspects of the Supreme Court's decision are likely to have implications within a Resource Management Act 1991 (RMA) context. Of particular importance are the Court's findings in relation to tikanga Māori.

The Supreme Court considered tikanga Māori was relevant to the DMC's decision on TTR's applications stemming from two sections of the EEZ Act. First, section 12 of the EEZ sets out how the Crown can achieve its responsibility to give effect to Te Tiriti principles. Secondly, section 59 provides that the DMC must take into account any effect on the environment or existing interests, including any applicable law.

In considering the application of section 12 of the EEZ, the Supreme Court found that a "broad and generous" approach was required and that the Treaty clauses should not be narrowly construed. The Supreme Court considered that a decision makers' ability to respect Te Tiriti principles should not be constrained unless Parliament makes that intention quite clear.

In accordance with section 59, the EEZ requires the decision maker to take into account effects of activities on "existing interests" in a way that recognises Crown obligations to give effect to Te Tiriti principles. The Supreme Court considered existing interests includes tikanga-based customary rights and interests. In this case, such existing interests included kaitiakitanga of relevant iwi as well as rights recognised, and rights claimed but not yet granted, under the Marine and Coastal Area (Takutai Moana) Act 2011 (MACA). Additionally, tikanga as law must be taken into account as "other applicable law" under section 59 by the decision maker "where its recognition and application is appropriate to the particular circumstances of the consent application at hand".

This decision has removed any ambiguity as to whether tikanga Māori is capable of applying as law. It is now important for decision makers to be asking themselves whether tikanga Māori is an applicable existing interest relevant to their decisions. In the context of the RMA, this may arise where sections 6(g), 7(a) and 8 of the RMA are relevant to decisions.

Section 6(g) of the RMA requires the protection of protected customary rights are recognised and provided for as a matter of national importance. Customary interests that exist, including those not legally recognised, could be afforded weight under the RMA given the Supreme Court's finding that rights claimed but not yet granted under the MACA were still existing interests.

The Supreme Court's findings may also indicate a broad interpretation of section 7(a) of the RMA which requires persons exercising functions and powers under the RMA to have particular regard to kaitiakitanga. Given the Supreme Court found that kaitiakitanga constitutes an "existing interest" and tikanga is "applicable law", RMA decision makers will need to be careful to have regard to kaitiakitanga where relevant.

Additionally, the decision indicates a general trend towards a broad and generous interpretation of section 8 of the RMA, as well as a greater recognition of Māori rights as defined by tikanga Māori and guaranteed under Te Tiriti o Waitangi.

Going forward, local authorities must keep informed to be in a position to recognise where tikanga Māori exists, and how it might affect its decision-making.