Formerly known as Other Government Agencies or OGAs, there are countless "Partner Government Agencies" that have an enforcement role either at the border or elsewhere within distribution channels. Many of these agencies have published their own import manuals, which can be found here.
Here's a quick hit list of what is regulated and by whom.
Food and Drug Administration (FDA)
FDA regulates a lot of products, more than what immediately comes to mind. The list includes foods, cosmetics, medical devices, drugs, tobacco, and dietary supplements. It also includes cups, plates, utensils, shampoo, makeup brushes, sponges, and compression apparel. Bottom line, they regulate anything that claims to treat or prevent disease, or affects the structure of the body, including the skin.
Food Safety and Inspection Service (FSIS)
Meat, poultry, or processed egg products. This agency is responsible for ensuring these products are safe, wholesome, unaltered and properly labeled and packaged.
Furniture, hardwood floors, instruments, hand tools, etc. Most articles made of wood must comply with the Lacey Act and require a PPQ Form 505 be completed.
Consumer Product Safety Commission (CPSC)
This agency works closely with U.S. Customs and Border Protection (CBP) to identify and examine imported shipments of consumer products. Your product could be on their target list, which includes children’s products containing excessive levels of lead, children’s sleepwear, toys and other articles with small and general use products such as mattresses, art materials, fireworks and lighters.
Department of Transportation (DOT)
Tires, exhaust systems, brake components, seats (including child seats), even parts designed principally for golf carts.
Environmental Protection Agency (EPA)
Toxic substances, chemical products, pesticides, nail polish, glow in the dark sticks, and pens are some examples of products regulated by this agency. In order to import, a TSCA Certification must be provided.
Fish & Wildlife Service (FWS)
Any products made of reptilian leathers, wildlife teeth, claws, and bird feathers are subject to FWS regulations and enforcement.
Alcohol and Tobacco Tax and Trade Bureau (TTB)
An arm of the Bureau of Alcohol, Tobacco and Firearms (ATF), the TTB regulates the import of tobacco, wines and spirits, firearms, and ammunition.
Keep in mind that the above list is a only a subset of all PGAs regulating imported merchandise. It is the importer’s responsibility to be aware of what they need to import a product. If a PGA refuses a shipment, CBP will consequently not allow the goods to enter U.S. commerce. If you have any questions concerning these regulations, contact us at firstname.lastname@example.org.