"A library designated by law to receive without charge all or a selection of the official publications of a government."  -Dictionary.com

"Governments at all levels have arrangements to get their publications to people.  Depository programs exist for states, the federal government, foreign governments and international organizations. The US version is the Federal Depository Library Program or FDLP. State and international organization depository programs are typically administered by headquarter libraries.  For example, the Dag Hammarskjöld Library, is the program manager for the United Nations depository program and the California State Library manages the California depository library program." 

-Forte, E. J., Hartnett, C. J., & Sevetson, A. (2016). Fundamentals of government information : mining, finding, evaluating, and using government resources. New York: Neal-Schuman Publishers. p. 45