Agreements between elements of the U.S. Government and representatives of foreign governments are subject to the Case-Zablocki Act, and several implementing regulations.
The Case-Zablocki Act itself can be found in 1 USC 112a and 1 USC 112b.
Regulations implementing the Case-Zablocki Act include:
22 CFR Part 181, Coordination, Reporting, and Publication of International Agreements (note: link points to 2006 version of the CFR).
DoD Directive 5530.3
CJCS Instruction 2300.01B