The Marine Mammal Protection Act (MMPA) was the first act of the United States Congress to call specifically for an ecosystem approach to wildlife management.

MMPA was signed into law on October 21, 1972, by President Richard Nixon and took effect 60 days later on December 21, 1972. It prohibits the "taking" of marine mammals, and enacts a moratorium on the import, export, and sale of any marine mammal, along with any marine mammal part or product within the United States. The Act defines "take" as "the act of hunting, killing, capture, and/or harassment of any marine mammal; or, the attempt at such." The MMPA defines harassment as "any act of pursuit, torment or annoyance which has the potential to either: a. injure a marine mammal in the wild, or b. disturb a marine mammal by causing disruption of behavioral patterns, which includes, but is not limited to, migration, breathing, nursing, breeding, feeding, or sheltering." The MMPA provides for enforcement of its prohibitions, and for the issuance of regulations to implement its legislative goals.

Authority to manage the MMPA was divided between the Secretary of the Interior through the U.S. Fish and Wildlife Service (Service), and the Secretary of Commerce, which is delegated to the National Oceanic and Atmospheric Administration (NOAA). Subsequently, a third federal agency, the Marine Mammal Commission (MMC), was established to review existing policies and make recommendations to the Service and the NOAA better implement the MMPA. Coordination between these three federal agencies is necessary in order to provide the best management practices for marine mammals.

Under the MMPA, the Service is responsible for ensuring the protection of sea otters and marine otters, walruses, polar bears, three species of manatees, and dugongs. NOAA was given responsibility to conserve and manage pinnipeds including seals and sea lions and cetaceans such as whales and dolphins.

The NOAA enforces the Marine Mammal Protection Act through the implementation and enforcement of various policies and regulations to properly manage marine mammal populations. The NOAA does this through the identification of violations of the MMPA, coordinating efforts to aid stranded and entangled mammals, and conduct proper rehabilitation and release of injured marine mammals. The NOAA is also responsible for providing stock assessment reports on marine mammals under their jurisdiction which includes whales, dolphins, porpoises, seals, and sea lions. Stock assessment reports serve to identify trends in marine mammal populations, identify potential threats to said population, and whether current conservation efforts are effective and if adjustments need to be made to ensure effective enforcement of the MMPA. The specific information that is included in all stock assessments are the geographic range of the stock being studied, current trends and productivity rates for the stock, potential biological removal levels which is defined under the MMPA as "the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population", an estimation of mortality and injury rate caused by humans, potential threats to conservation efforts and current status of the stock and a minimum population estimation. These stock assessments are created through research conducted by programs at NOAA research science centers which are located in Hawaii, Massachusetts, Alaska, Florida, Washington, and California. Research contributions are also made by researchers not affiliated with the previously mentioned programs as well.

The Marine Mammal Commission (MMC) was created in 1972 through the MMPA to serve as an organization that provides oversight over conservation policies, regulations and programs being carried out to ensure they are carried out effectively by the federal agencies responsible for them. Their responsibilities also include ensuring the United States adhere to international agreements that relate to marine mammal conservation "including, but not limited to, the International Convention for the Regulation of Whaling, the Whaling Convention Act of 1949, the Interim Convention on the Conservation of North Pacific Fur Seals, and the Fur Seal Act of 1966." The MMC is also responsible for the review of the research programs conducted for the purpose of the MMPA as well as authorizing permits for the purpose of research, conservation or public display. If the MMC finds that the current conservation efforts are shown to be ineffective in protecting species identified under the MMPA, they are responsible for effectively communicating with federal officials such as the Secretaries of State, Commerce or the Interior the recommended measures needed to be taken to ensure the effectiveness of the MMPA and the protection of marine mammals under this act. These recommendations can come in the form of implementation of international agreements, revisions to the endangered and threatened species list as deemed appropriate under the Endangered Species Act of 1973, and provisions that may need to be made to the MMPA.  

The U.S. Fish and Wildlife Services are responsible for managing the take through the use of permits and other authorization as well as financially supporting efforts to help marine mammals that fall victim to stranding and relevant research efforts. Similar to the NOAA, the U.S. Fish and Wildlife Services conduct stock assessments of marine mammal populations under their jurisdiction which include walrus, manatees, sea otters, and polar bears. They are also responsible for the creation and implementation of conservation plans which often occur in collaboration with industries which can potentially impact marine mammal populations of particular concern.

The MMPA prohibits the take and exploitation of any marine mammal without appropriate authorization, which may only be given by the Service. Permits may be issued for scientific research, public display, and the importation/exportation of marine mammal parts and products upon determination by the Service that the issuance is consistent with the MMPA's regulations. The two types of permits issued by the National Marine Fisheries Service's Office of Protected Resources are incidental and directed. Incidental permits, which allow for some unintentional taking of small numbers of marine mammal, are granted to U.S. citizens who engage in a specified activity other than commercial fishing in a specified geographic area. Directed permits are required for any proposed marine mammal scientific research activity that involves taking marine mammals.