From the Document: "Law enforcement officials in the United States and abroad frequently seek access to electronic communications, such as emails and social media posts, stored on servers and in data centers in foreign countries. Because the architecture of the internet allows technology companies to store data at a great distance from the physical location of their customers, electronic communications that could serve as evidence of a crime often are not housed in the same country where the crime occurred. This disconnect has caused both the United States and foreign governments to seek access to data stored outside their territorial jurisdictions. In the Clarifying Lawful Overseas Use of Data (CLOUD) Act, Congress enacted one of the first significant changes in decades to U.S. law governing cross-border access by law enforcement to electronic communications held by private companies. [...] The CLOUD Act has two major components. The first facet addresses the U.S. government's ability to compel technology companies to disclose the contents of electronic communications stored on the companies' servers and data centers overseas. [...] The second facet [...] addresses the reciprocal issue of foreign governments' ability to access data in the United States as part of their investigation and prosecution of crimes."
CRS Legal Sidebar, LSB10125
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html