SEOUL, South Korea (AP) — South Korea's top court has ruled that people can legally reject mandatory military service on conscientious or religious grounds and must not be punished.

The landmark ruling Tuesday is expected to affect the cases of more than 900 conscientious objectors on trial.

Hundreds of South Koreans, mostly Jehovah's Witnesses, are imprisoned every year for refusing to serve in the military.

The Supreme Court said it quashed a lower court's ruling that sentenced a conscientious objector to 18 months in prison. It says it ordered the lower court to review its earlier verdict.

Earlier this year, South Korea's Constitutional Court ruled the government must introduce alternative social service for conscientious objectors by 2019.