From the Document: "This report reviews the process and procedures that currently apply to congressional consideration of foreign arms sales proposed by the President. This includes consideration of proposals to sell major defense equipment, defense articles and services, or the retransfer to other states of such military items. In general, the executive branch, after complying with the terms of applicable U.S. law, principally contained in the Arms Export Control Act (AECA) (P.L. 90-629, 82 Stat. 1320), is free to proceed with an arms sales proposal unless Congress passes legislation prohibiting or modifying the proposed sale. The President has the obligation under the law to submit the arms sale proposal to Congress, but only after he has determined that he is prepared to proceed with any such notifiable arms sales transaction. The AECA also contains the statutory authority for the Foreign Military Sales (FMS) program, under which the U.S. government sells U.S. defense equipment, services, and training on a government-to-government basis. In addition, the law specifies criteria for Direct Commercial Sales (DCS) of U.S.-government licensed defense articles and services directly from U.S. firms to eligible foreign governments and international organizations."
CRS Report for Congress, RL31675
Congressional Research Service: https://crsreports.congress.gov/