https://en.m.wikipedia.org/wiki/Letter_of_marque
The issue of marque and reprisal was raised before Congress after the September 11 attacks and again on July 21, 2007, by Congressman Ron Paul. The attacks were defined as acts of "air piracy" and the Marque and Reprisal Act of 2001 was introduced, which would have granted the president the authority to use letters of marque and reprisal against the specific terrorists, instead of warring against a foreign state. The terrorists were compared to pirates in that they are difficult to fight by traditional military means. On April 15, 2009, Paul also advocated the use of letters of marque to address the issue of Somali pirates operating in the Gulf of Aden. However, the bills Paul introduced were not enacted into law.