ISIS Influence on Web Prompts Second Thoughts on First Amendment

David G. Post, a former professor of constitutional law who is a senior fellow at the Open Technology Institute of the New America Foundation in Washington, was one of many legal experts to condemn Mr. Posner’s idea.

“I think it is a slippery slope,” Mr. Post said in an interview. In a law blog, The Volokh Conspiracy, he wrote that efforts to suppress radical views “can be far too easily twisted into a prohibition against dissenting viewpoints.”