The truck allegedly had "a catastrophic mechanical failure," according to the Seattle Police Department.
The measure signed by Gov. Gavin Newsom will change California's existing standards to require that deadly force may only be used when necessary.
An administrative judge had earlier recommended that Pantaleo be terminated. Garner's death, which sparked national protests, occurred on July 17, 2014.
Police believe the attack was targeted: "We do not believe there is a random stabber."
The two men claim that the October 2018 incident, when they beat four antifa protesters after an appearance by the Proud Boys' founder at a Republican club, was self defense.