The substantive law of the World Trade Organization (WTO) partakes more of the nature of a code than of a detailed regulatory system for state conduct in the sphere of international trade. The WTO code sets out a broad framework within which member states need to conduct their affairs. The code is aimed at eliminating discrimination in government regulations relating to international trade in goods and services and reducing and/or eliminating barriers to the flow of such international trade. The principle of non-discrimination is a fundamental tenet of the international trading system. The tariff is the principal form of tolerated policy instrument under the WTO code. Quantitative restrictions and tariffs are border control measures. The obligations under the WTO code in relation to these measures can be undermined through customs and allied procedures. The sanitary and phytosanitary measures must be based on scientific principles, and not be arbitrary.