U.S. Supreme Court critics are highlighting Justice Samuel Alito’s behavior on the bench last week—specifically his eye rolls and head shakes—as a prime example of why the nation’s highest court needs some more rules.

Alliance For Justice, a liberal watchdog group, has linked Alito’s physical reactions last week’s opinion readings to the need to subject Supreme Court justices to the Code of Conduct for United States Judges. The code, which guides the behavior of lower federal court judges regarding recusals, fundraising and demeanor, has never applied to the justices themselves, although they have said that they look to it for guidance.