Title 21 of the US Code of federal regulations (
21 CFR) lists all of the ingredients approved for use in the US food supply, whether for humans or animals. The US is a net exporter of corn and soy, and China is a net importer, so your example is not the best but I get your point.
More importantly, so does the FDA. They are currently working on the second draft of the proposed rules to cover verification that imported food products are produced to US standards as part of the Food Safety Modernization Act (
FSMA). FSMA is the most extensive revision of US food and feed laws since the original 1938 Federal Food Drug and Cosmetics Act. One of the proposed regulations is to cover Foreign Supplier Verification, by which importers must certify (through inspections) that foreign companies are following the same rules as US based companies when producing their products for export to the US. Furthermore, the FDA plans to begin on-site inspections of foreign sites at a minimum of every 3 years. For those sites that are classified as a higher risk level, they will be inspecting every year, and only the first inspection is free. The FDA will bill the company for the cost of follow up inspections if problems are found and a re-inspection is deemed necessary.
Also, FSMA gives the FDA vast new enforcement powers. Currently, they can recommend a product recall, but the manufacturer ultimately decides. Once the act is in place, they will be able to sieze all product in the supplychain, issue recalls, and close down manufacturing sites on the
suspicion of a problem. They don't need to have any hard evidence like testing data or sick people.