The Arms Export Control Act (AECA) is the formal legislation behind the USG FMS program. It was established in 1976 and gives the President of the United States (POTUS) the authority to control the import and export of defense articles and defense services. The legislation authorizes the following:
 

• Letters of Offer and Acceptance (LOAs), aka FMS cases
• Government-to-government agreements
• Including the sale of defense articles, services, and training
  • From Department of Defense (DoD) stock
  • Through new procurements under DoD managed contracts 

A Letter of Request (LOR) is a document submitted from a Partner Nation to the USG requesting permission to purchase a particular defense article and/or service. An authorized representative of a Partner Nation must submit LORs in writing via an email, memo, or signed meeting minutes to an authorized representative of the USG. The LOR must be considered complete and actionable per the electronic Security Assistance Management Manual (eSAMM) Chapter 5, C5.1.2 & C5.1.3).

A Letter of Offer and Acceptance (LOA) is a formal country-to-country agreement developed by the Air Force Security Assistance and Cooperation (AFSAC) Directorate in response to a complete and actionable LOR from a Partner Nation. Once a Partner Nation signs an LOA and provides initial funding, the AFSAC Directorate works with the Partner Nation and appropriate AFMC FMS Enterprise Organizations to execute the case.