National security in an age of massive movements of people across borders is a universal concern that involves complex issues. While borders have different characteristics and challenges, there are areas of commonality. Fortunately, the overwhelming majority of crossings are not problematic, but the ones that are raise concerns.

On Dec. 5, 2011, MIT Associate Professor of Political Science Chappell Lawson, who recently completed a two-year assignment as executive director and senior advisor to the commissioner of U.S. Customs and Border Protection, offered his thoughts on homeland security and answered questions from the worldwide MIT alumni community. Watch the video then join the discussion online.