Code of Federal Regulations Citation. Office of International Investment, Department of Treasury -- Regulations pertaining to mergers, acquisitions, and takeovers by foreign persons, 31 CFR Part 800.
A good article to start with:
http://www.marketwatch.com/News/Story/Story.aspx?guid=%7B0317AEEE%2D47AF%2D42BD%2DBEFF%2D260274800569%7D&siteid=google&keyword=
http://www.treasury.gov/offices/international-affairs/exon-florio/
Thank you for those links.