The ACT Party has released a policy it says is designed to protect core democratic values and property rights, reign in "activist judges" and stop Parliament creating divisive Treaty of Waitangi clauses.

"Today's policy is about ensuring New Zealanders can move forward under one law for all with one future together," party leader David Seymour said.

"ACT will add three principles to the Constitution Act, affirming the basic values that Parliament is sovereign, the rule of law is fundamental and all New Zealanders are equal before the law."

Key to the policy is restraining courts from considering Māori tikanga (custom) in decisions.

"Recent Supreme Court decisions have pushed the line further than Parliament ever legislated," Seymour said.

"Parliament has pushed back in some instances, such as Smith v Fonterra and the Marine and Coastal Area cases, but others, such as Ellis, where the Supreme Court widely expanded the use of tikanga in the law, have not been responded to.

"Parliament is elected, judges are not. We cannot allow tikanga to become a separate source of law applying to broad areas of unrelated law without Parliament ever deciding that it should.

"ACT will make clear that tikanga cannot be used to influence court decisions, except where Parliament has expressly allowed for it."

The party would also amend the Legislation Act 2019 to ensure statutes are enacted in the context of the time they were passed. Judges could resolve ambiguity, but not override statutory language.

"Courts are often responding to unclear legislation or Parliament's silence, when they make decisions that substantially change how the law is understood.

"ACT will stop governments writing vague treaty clauses into law that create uncertainty, and leave courts and officials to decide what they mean through divisive interpretations."

Any bill referring to the Waitangi Treaty would require cabinet to agree which interests were engaged, who they apply to and what obligations they created, restoring "clear lines of democratic accountability".

"We won't unlock New Zealand's potential while the political and judicial classes experiment on our basic rights," Seymour said.

"Inventing new legal concepts, dividing us according to some people's version of history and trampling our property rights might be fun for wig wearers in court and lanyard wearers in the public service, but all it does for the ordinary person is created uncertainty and frustration

The full policy can be viewed here.