Feinstein has practiced matrimonial and appellate law since 1980, having obtained his JD degree from Emory University (a "Top 20" Law School) in Atlanta, Georgia. He became a fellow of the prestigious American Academy of Matrimonial Lawyers in 1991. He belongs to the Family Law Sections of the American, Illinois, and Georgia bar associations. He was admitted to the Appellate Lawyers Association
in 2010. He is licensed to practice in Illinois and Georgia, as well as the United States Supreme Court. He has written about numerous matrimonial law subjects and is currently on the board of editors of the Matrimonial Strategist, a national publication. He has also lectured before several groups on many family law topics. He devotes a great deal of his practice to appellate and constitutional law and in 1993 was successful in overturning Illinois' automatic asset freeze law in the Supreme Court of Illinois. In 2004, he was successful in having the Supreme Court of Illinois declare the Illinois Child Representative Statute unconstitutional. He returned to the Supreme Court of Illinois in 2012 and was again successful, this time overturning an Appellate Court ruling concerning the definition of income for purposes of child support cases. He handles all litigation aspects of family law issues, including divorce, custody, domestic violence, premarital agreements, and parentage. He also is often called upon to consult in cases which may be going to trial.