The government bans the import of plastic waste, the narcotic plant “qat”, diesel passenger cars and freight cars intended for transporting goods manufactured ten or more years ago, not including trailers and semi-trailers.  Exporters should always note that U.S. export licenses, though not required for many shipments, are required in certain situations involving national security, foreign policy, short-supply, nuclear non-proliferation, missile technology, chemical and biological weapons, regional stability, crime control, or terrorist concerns.  For more information on export licenses, please refer to U.S. Export Licenses: Navigating Issues and Resources (trade.gov) at https://www.trade.gov/us-export-licenses-navigating-issues-and-resources.