What is considered the most important counter terrorism law ever passed by Congress

Privacy act, anti patriot act, patriot act, surveillance act

The correct option is:

Patriot Act

Explanation:

Patriot Act was passed just 45 days after the incident of 9/11. Main purpose of the act was to improve National Security, and punish terrorist activities in USA and around the globe. Many successful operation have been carried out under the shadow of Patriot Act, to protect the American citizens from deadly plans of terrorists. It also made it easier for the American government to spy on its citizens, by expanding their authority in the communications.