Access to Government Information in the United States: A Primer--Congressional Research Service (March 18, 2016 ed.)
Summary from CRS document:
"The U.S. Constitution makes no specific allowance for any one of the three branches of the federal government to have access to information held by the others. No provision in the U.S. Constitution expressly establishes a procedure for public access to government information.
Congress has legislated various public access laws. Among these laws are two records access statutes,
• the Freedom of Information Act (FOI Act or FOIA; 5 U.S.C. § 552), and
• the Privacy Act (5 U.S.C. § 552a),
and two meetings access statutes,
• the Federal Advisory Committee Act (FACA; 5 U.S.C. App.), and
• the Government in the Sunshine Act (5 U.S.C. § 552b).
The American separation of powers model of government may inherently prompt interbranch conflicts over the accessibility of information. These conflicts are neither unexpected nor necessarily destructive. Although there is considerable interbranch cooperation in the sharing of information and records, such conflicts over access may continue on occasion.
This report offers an overview of the four information access laws noted above, and provides citations to additional resources related to these tools."