FISA "Vital" to National Security

ABC News Crime & Terrorism Analyst Brad Garrett talks about how Section 702 of the Foreign Intelligence Surveillance Act authorizes U.S. Intelligence agencies collect communications from non-U.S. citizen targets overseas to include U.S. citizens if they are communicating with the foreign target without a warrant. What is the issue with the collection of FISA intelligence? Why is there a controversy, but also why is it critical to protecting the country?