The Canadian and United States' approaches to oversight of animals in research are both based on the "3Rs" principles outlined in Russell and Burch's classic text, The Principles of Humane Experimental Technique. Each country seeks to protect the welfare of animals, while permitting the legitimate goals of scientific research to be attained according to the legal principles, cultures, and strengths and constraints of their jurisprudential and societal traditions. Canada is one of the most decentralized federations in the world, and regulation of activities is based to a great extent on custom and practice. The United States is more hierarchical and, at least with respect to laws governing animal research, more centralized. Accordingly, the Canadian approach is rooted in the concepts of social contracts, with a greater emphasis on guidance and policy and less reliance on legislation. No federal (national) direct legislation of laboratory animal welfare exists, although the federal government uses its criminal and spending authorities to shape behavior. The central feature of the Canadian system is the Canadian Council on Animal Care, which was formed to support universities and government departments involved in animal-based science. Animal care committees play a central role in implementing the guidelines and policies in facilities that carry out animal research. The United States has enacted two federal (national) laws applicable to animals in research. The Animal Welfare Act is a more traditional, command-and-control law that gives authority to the US Department of Agriculture to promulgate regulations, inspect facilities, and enforce violations. The Health Research Extension Act, which amended the US Public Health Services (PHS) Act, applies to any activity conducted or supported by the PHS, including research efforts supported by the US National Institutes of Health. It is largely nonregulatory and establishes a system of assurances and policies that covered research facilities must follow. States play only a minor role in animal research protection. As in Canada, institutional animal care and use committees are tasked with self-regulation of activities that use animals for research.