 Since the 1940s, the Jehovah's Witnesses have often invoked the First Amendment's freedom of religion clauses to protect their ability to engage in the proselytizing (or preaching) that is central to their faith.This series of litigation has helped to define civil liberties case law in the United States and Canada.In the United States of America and several other countries, the legal struggles of the Jehovah's Witnesses have yielded some of the most important judicial decisions regarding freedom of religion, press and speech.