Each person who has engaged in foreign commerce grain business totaling 15,000 or more metric tons during the preceding or current calendar year must register with the Service and shall be deemed to be regularly engaged in foreign commerce grain business. This includes foreign-based firms operating in the United States but does not include foreign governments or their agents. The Service will, upon request, register persons not required to register under this section if they comply with the requirements of §§ 800.33 and 800.34.