On the 25th of November, 1775, the Continental Congress authorizes privateering.
http://www.navy.mil/search/display_history.asp
http://www.history.navy.mil/wars/datesnov.htm

Other sources show that on March 23, 1776, Congress formalized the privateering commissioning process.

For more on U.S. Privateering:
http://www.nps.gov/revwar/about_the_...rivateers.html
http://founders.archives.gov/documen...3-02-0016-0083
http://penelope.uchicago.edu/Thayer/...CHITAP/8*.html
http://www.shsu.edu/~his_ncp/Privat.html
http://web.massar.org/privateers-of-the-revolution/
http://www.1812privateers.org/United...tes/USgov.html