Viewpoint discrimination is the term the Supreme Court has used to identify government laws, rules, or decisions that favor or disfavor one or more opinions on a particular controversy.
http://digitalcommons.law.yale.edu/cgi/viewcontent.cgi?article=5649&context=fss_papers
http://scholarship.law.duke.edu/cgi/viewcontent.cgi?article=2956&context=faculty_scholarship
paul statchen 