Sacramento County Superior Court Judge Lloyd Connelly ruled in Schwarzenegger's favor on Friday in the case of Esteban Nunez, son of former Assembly Speaker Fabian Nunez.
The younger Nunez pleaded guilty to voluntary manslaughter in a 2008 attack on an unarmed group of young men after he and some friends were turned away from a fraternity party in San Diego. Three others pleaded guilty to various charges in the attack that killed 22-year-old college student Luis Santos.
Nunez received a 16-year sentence, but Schwarzenegger commuted the sentence to 7 years, just hours before leaving office.
The Santos family and the San Diego District Attorney sued, saying it violated Marsy's Law, which requires families to be notified of shortened sentences.
Lloyd Connelly called the former governor's decision distasteful and "repugnant to the bulk of the citizenry of this state," but said it didn't violate the law.
Nunez's mother was upset by the decision.
"She thinks it's outrageous. She's very disappointed. She believes there's political corruption involved. She has the right to be appalled at the ruling today and what Schwarzenegger did," said San Diego Deputy District Attorney Laura Tanney.
The judge said Marsy's Law only applies to pardons not commutations, and he felt he had no choice but to let the reduced sentence stand. The district attorney plans to appeal the ruling.
Schwarzenegger said in his commutation notice that he believed the sentence was excessive given Nunez's "limited role in the killing." He said evidence showed that Nunez's friend delivered the fatal blow, yet both men received the same 16-year sentence.
The former governor told Newsweek in April 2011 that his office made a mistake in not notifying Santos' parents, but he defended the decision, saying: "I mean, of course you help a friend." Schwarzenegger also issued a formal apology to the Santos family.
Last year, Gov. Jerry Brown signed a bill written in response to the controversy. It requires at least 10 days' notice for commutations as well.