SEOUL (NYTIMES) - South Korea's Supreme Court on Thursday (Nov 1) acquitted a man who refused to serve in the military because of his religious beliefs, a ruling expected to affect the fate of more than 900 conscientious objectors who refused mandatory service in the country's armed forces.

For decades, South Korea has required all able-bodied men in South Korea to serve in the armed forces and granted few exemptions under a conscription system seen as crucial to the country's defence against North Korea.

It has billed military service as a patriotic duty, and the punishment of those who refused to serve has been both uniform and harsh. Each year, South Korea has sent hundreds of young men, most of them Jehovah's Witnesses, to prison by invoking its Military Service Act, which calls for up to three years in prison for those who refuse to serve without "justifiable" reasons.

On Thursday, the Supreme Court for the first time accepted "conscience or religious beliefs" as such a justifiable reason, while overturning a lower court ruling in which a Jehovah's Witness was sentenced to 18 months in prison.

The country's Constitutional Court had already objected to the decades-old practice of imprisoning conscientious objectors. In June, it ruled that the failure to offer alternative forms of civilian service to conscientious objectors was unconstitutional, and gave the government until the end of next year to introduce the option of performing alternative services, like working in prisons or fire stations.

But the fate of conscientious objectors already on trial had been in limbo until the Supreme Court's ruling on Thursday.

"Today's ruling is a great comfort for nearly 20,000 conscientious objectors in South Korea who have had to live with the stigma of being ex-convicts for the past 65 years," said Hong Dae-il, a spokesman for Jehovah's Witnesses in South Korea.

Even before the Constitutional Court and Supreme Court rulings, lower court judges had recently shown increasing reluctance to send conscientious objectors to jail.

Since 2004, the lower courts have found 118 conscientious objectors innocent. Many other lower court judges have delayed ruling on pending cases, asking for an authoritative decision from the two top courts.

Until now, South Korea has prosecuted more young men for conscientious objection than any other country, and it was one of the few that treated it as a crime without offering a different form of national service. Amnesty International and the Jehovah's Witnesses say more than 19,300 South Korean conscientious objectors have gone to prison since the 1950-53 Korean War.

South Korea's border with North Korea is the most heavily armed frontier in the world, and the two countries are technically still at war. North Korean men typically serve in the country's military for a decade. Some South Koreans fear that legalising conscientious objection will undermine the country's national defence.

President Moon Jae-in of South Korea has worked to ease military tensions and improve ties with North Korea. When Moon met with Kim Jong Un, North Korea's leader, in September, they agreed to institute "no-fly" zones, as well as impose a halt to military training near their land and sea borders starting on Thursday.

Speaking to the National Assembly on Thursday, Moon said that through his three summit meetings with Kim this year, he has "completely removed the danger of military clash" and set the stage for expanding economic and other ties with North Korea. He also said he hoped Kim would keep his promise to visit Seoul "soon".

"This is an opportunity that has come like a miracle and we should never miss it," he said.

Moon has been under pressure from Washington and his conservative foes at home not to take inter-Korea relations too far before North Korea starts dismantling its nuclear weapons programme.

Both South Korea and the United States have agreed to coordinate their approaches on North Korea. But Seoul wants to improve inter-Korea ties quickly to help build trust and encourage North Korea to denuclearise, while Washington insists on enforcing sanctions as leverage against the North. Unless those sanctions are lifted, Moon's room to manoeuvre on expanding inter-Korea ties is limited.