Member nations of the World Trade Organization are permitted to develop regulations that might restrict trade if they do so for the purpose of protecting human, animal or plant life or health. The regulations, under both the Sanitary/Phytosanitary and Technical Barriers to Trade agreements, must be based on science, be non-discriminatory and be the least-trade-restrictive alternative. Uncertainty, a lack of adequate scientific evidence and differing interpretations have led to disputes about regulations applied by particular countries. If consultations cannot resolve the issues, dispute settlement panels and an appellate body adjudicate them; in these forums, scientific knowledge, studies and testimony by scientists play key roles.