In the United States, a customs inspector works for the Department of Homeland Security, which is a branch of the federal government. In other countries, customs inspectors work for the government under different program titles. They enforce the laws of the land that control the imports and exports that are allowed into and out of the country. They help to protect against terrorists and terrorist activities by the inspection of travelers coming in and out of the country and by inspecting cargo. The inspector works with all types of law enforcement agencies, both on the state and national level, to find potential threats, illegal substances, and even illegal travelers.

Customs inspectors work with many different law agencies including the FBI, the Drug Enforcement Administration. When inspecting cargo, a customs inspector may work with freight companies and other types of agencies to verify the cargo contents before allowing them into the country. The inspector is responsible for inspecting all of the cargo, viewing the documentation of the cargo, and clearing the cargo for release. The inspector is also responsible for finding potentially hazardous materials or unlawful contents in the cargo to prevent them from being brought illegally into the country.

All countries have their own form of customs inspectors and they all vary slightly in their responsibilities. Many countries require their customs inspectors to be armed to prevent threats that can try to invade the country. It is important to understand a country's laws on customs inspectors so that one knows what to expect in this field.