The law of New Zealand consists of the common law, certain statutes of the United Kingdom Parliament, statutes of the New Zealand Parliament, and regulations, bylaws, and other forms of subordinate legislation made under statutory authority. International law, although it binds New Zealand in its relations with other countries, is not part of our law. A treaty entered into by this country has no legal effect internally. If it is to become part of the law of the land it must be embodied in a statute.

The common law, sometimes referred to as case law or Judge-made law, has been built up over the centuries by the Courts in England and, later, in New Zealand and other countries where it was introduced. Like any living law, the common law continues to develop. It is still occasionally said that the Courts do not make new law, but merely declare what the law has always been. By any practical test, however, the decisions of the Courts alter and add to the law. Most of the law of tort, for instance, is the creation of the last 100 years.

In New Zealand the policy of the Courts has been to preserve uniformity with the common law in England. This is partly for reasons of convenience and partly because of the assumption prevailing in New Zealand that there is a single common law, the law of England, and that there are not separate, though similar, common laws in different countries.

United Kingdom statutes in force in New Zealand comprise those passed before 1840 which were applicable to the circumstances of the colony at that date, and those passed between 1840 and 1947 which extended to New Zealand expressly or by necessary implication. Many of these statutes have, of course, since been repealed. In 1947 New Zealand adopted the Statute of Westminster, and our Parliament has since been the sole authority with inherent power to legislate for the country. There are no constitutional restrictions on the laws Parliament can pass. Formerly its powers were limited. First, there was a somewhat uncertain and ill-defined incapacity to make laws applying outside the country. Secondly, there was an incapacity to make laws conflicting with a United Kingdom Act extending to New Zealand. Both limitations disappeared in 1947. The United Kingdom Parliament has, however, power to make laws extending to this country at the request and with the consent of the Parliament of New Zealand. The making of such a request in future is most improbable.

Jurists have argued whether an Act passed by the British Parliament, which purported to extend to New Zealand in disregard of the Statute of Westminster, would be in force here. The question is, however, purely academic. If such legislation were passed it would doubtless be nullified by New Zealand legislation.