The United States Flag: Federal Law Relating to Display and Associated Questions was updated July 5, 2007. John R. Luckey, Legislative Attorney, American Law Division of the Congressional Research Service was the author of this CRS report to Congress.
The eighteen (18) page PDF file includes the U.S. Flag Code in its entirety as well as explanations of additions to the Code. Luckey begins with a Summary section, then follows with the Background and History of the Flag Code.
He covers Supreme Court rulings concerning First Amendment Rights, as well.