The National Counterterrorism Center issued a 166-page document to give watchlisting guidance The more worrying aspects involve getting around reasonable suspicion. As weve seen in the past, theres nothing reasonable about supposedly suspicious activities as numerous you-might-be-a-terrorist-if lists are often filled with harmless behaviors. Americans are protected by the First Amendment; the guidelines do say that constitutionally-protected activities cannot be the basis for nominating a person to be added to watchlists.”]
Source: https://www.csoonline.com/article/2458621/facebook-posts-can-land-americans-on-watchlists.html