During the 2016 debates, Clinton repeatedly stated that anyone on the terrorist watch list should not be able to purchase a gun . Senator Diane Feinstein proposed legislation to do exactly this in 2015, but it lost with a vote of 45-54 . Afterwards, Senators Susan Collins and Heidi Heitkamp proposed a bill that would ban gun sales to people on the shorter “no-fly list”; this bill was also defeated . On the face of it, these efforts look like an attempt to keep guns out of the hands of terrorists. Additionally, you may be one of the many millions of Americans who are in favor of increased gun control. So what’s wrong with this?
It comes down to the criteria that our government is using to place people on the terror watch list. People are placed on the list without a trial and without any due process (though travelers can challenge placement on the list due to the Travelers Redress Inquiry Program, a law passed in 2007 ). Thanks to the reporting of Glenn Greenwald and Laura Poitras, we now know that there are approximately 3 million people on the terror watch list .
By stating that anyone on the terror watch list should be prevented from purchasing a gun, Clinton and others were stating that the government should have the authority to arbitrarily remove an American citizen’s right to own a gun. Theoretically, the FBI could place everyone on the terror watch list and prevent everyone from purchasing a gun. This would be a complete subversion of the 2nd Amendment.
The constitution provides Americans with the right to purchase guns. Clinton’s hope to permit the federal government to eliminate that right at will was unconstitutional. The American Civil Liberties Union sent a letter to the senate regarding this issue ; from their letter,
Regulation of firearms and individual gun ownership or use must be consistent with civil liberties principles, such as due process, equal protection, freedom from unlawful searches, and privacy.
If you are one of the many Americans that feels that increased gun control (or the elimination of gun ownership) would be a good thing, then the only constitutional approach to achieving this goal would be to amend the Constitution, which would require a 2/3 vote of passing in both the senate and the house.
 First 2016 Presidential Debate, https://www.youtube.com/watch?v=Xy3zAn-Qyf0
 Jansen, B. “America’s Terror Watch List, Explained.” http://www.usatoday.com/story/news/2016/06/14/no-fly-list/85867624/
 Krieg, G. “Breaking Down the Terror Watch Lists: What’s the Difference?” http://www.cnn.com/2016/06/23/politics/terrorist-no-fly-watch-list-explained/
 Poitras, L. “Citizenfour”
 Shamsi, H. Anders, C. “The Use of Error-Prone and Unfair Watchlists is not the way to Regulate Guns in America.” June, 2016, https://www.aclu.org/blog/washington-markup/use-error-prone-and-unfair-watchlists-not-way-regulate-guns-america