Thomas I. Emerson, 83, an authority on the First Amendment who stood up against McCarthyism, died Wednesday of complications from a stroke in New Haven, Conn. A professor emeritus of law at Yale University, Mr. Emerson died at the Yale Health Services Center. His early career was spent in vTC Washington as a New Dealer, serving in a variety of legal posts for the Roosevelt administration. His opposition to abuse of government power during the McCarthy era led the FBI to order a secret file kept on him. He refused to quit as president of the National Lawyers Guild in 1950-51 after it was labeled a communist front. In 1965, he successfully argued a challenge to Connecticut's birth-control law before the U.S. Supreme Court. In that case, the Supreme Court for the first time recognized a constitutional right to privacy. His 1970 book, "The System of Freedom of Expression," was a landmark work on free speech. In 1984, he was named the first recipient of the American Civil Liberties Union's Medal of Liberty for his lifetime service in defense of civil liberties.