"The Committee on Foreign Investment in the United States (CFIUS) is an interagency body comprised of nine Cabinet members, two ex officio members, and other members as appointed by the President, that assists the President in overseeing the national security aspects of foreign direct investment in the U.S. economy. [...] The U.S. policy approach to international investment traditionally has been to establish and support an open and rules-based system that is in line with U.S. economic and national security interests. The current debate over CFIUS reflects long standing concerns about the impact of foreign investment on the economy and the role of economics as a component of national security. [...] Changes in U.S. foreign investment policy have potentially large economy-wide implications, since the United States is the largest recipient and the largest overseas investor of foreign direct investment. To date, only three investments have been blocked by previous Presidents, although proposed transactions may have been terminated by the firms involved in lieu of having a transaction blocked. President Obama used the FINSA [Foreign Investment and National Security Act of 2007] authority in 2012 to block an American firm, Ralls Corporation, owned by Chinese nationals, from acquiring a U.S. wind farm energy firm located near a DOD facility and to block a Chinese investment firm in 2016 from acquiring Aixtron, a Germany-based firm with assets in the United States."
CRS Report for Congress, RL33388
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html