For decades, the rule has been simple and unforgiving: If you are a South Korean man of able body, you must serve in the military or go to prison for up to three years.
Each year, hundreds choose prison -- nearly all for religious reasons -- giving South Korea one of the world's largest populations of imprisoned conscientious objectors.
Yoon Yeo-beom, a 24-year-old Jehovah's Witness whose faith forbids him from taking up arms, thought he would be among them when he ignored his draft orders this spring.
But Yoon and about 300 other objectors are now at the center of a legal battle that threatens to undermine universal conscription, a decades-old cornerstone of national defense against communist North Korea and an unwritten right of passage for young men in the South.
The rulings, beginning with Thursday's at the Supreme Court, could force the National Assembly to revise or abolish the country's strict prohibition against conscientious objection. Human rights groups say they could mark an advancement for religious freedom; critics say they could open the floodgates to draft dodging.
The Supreme Court has ruled against conscientious objectors in the past, as recently as 1992, but a separate case before the Constitutional Court will be a first there.
A landmark ruling by a Seoul district court in May freed three Jehovah's Witnesses, saying faith was ground for refusal. The ruling is being challenged by the government, but it has bolstered other appeals.
"I hope society will become less regimented and more willing to accept people like me," says Yoon, who was sentenced to 1 1/2 years but is currently free while a court hears his appeal.
A positive ruling Thursday would strengthen Yoon's case.
The crux of the question is an apparent legal inconsistency within the South Korean constitution, which mandates military service but also guarantees the freedom to act according to one's conscience.
For decades, national defense has been a top priority in South Korea, which is still technically at war with the North after the 1950-53 Korean War ended with a shaky truce.
Before reaching 30, all physically fit men must serve 24 months in the South's 650,000-member military, which faces off against the North's 1.1-million-member armed forces across the world's most heavily armed border.
Since the 1940s, an estimated 10,000 Jehovah's Witnesses, including Yoon's elder brother, have been sent to military prisons for rejecting the conscription law.
But the quandary of conscientious objectors has only recently become a focus of concern.
The number of newly declared conscientious objectors has climbed from 233 in 1994 to 705 in 2003, according to figures compiled by Lawyers for a Democratic Society, a leading human rights group in South Korea.
Today, South Korean prisons hold 440 objectors, most of them Jehovah's Witnesses.
Jailed objectors have testified in the past to beatings, sleep deprivation and other brutal treatments.
Their criminal records later bar them from working in big businesses and the government. They also face prejudice in a society versed in the maxim: "You can't be treated as a man unless you have served in the military."
"We could not talk about it. No one cared," said Hong Young-il, a Jehovah's Witness jailed from 1990-1992.
Hong, once a promising electronic engineering major at the elite Seoul National University, declared himself a conscientious objector in boot camp.
"They gave me a rifle. I refused to accept it. They gave it again, and I refused again. After a two-minute court session, they convicted me of rebellion," Hong said.
Out of prison, Hong could only land a door-to-door sales job and petty work.
Ironically, the fate of Jehovah's Witness inmates only drew nationwide attention in 2001, when a Buddhist became the first non-Jehovah's Witness to declare himself a conscientious objector.
Since then, 14 other pacifists have either been jailed or are on trial.
With the government seeking reconciliation with former battlefield foe North Korea, conscientious objectors say it's time to allow them "alternative" civil service, such as working in homeless shelters.
The Defense Ministry calls that an unfair privilege. It says "tolerating conscientious objection would threaten the very existence of our nation," especially amid tension's over North Korea's nuclear weapons program.
The ministry also worries it will fan an increasing trend of draft dodging among the less spiritual.
Repeated scandals show many of the country's rich and powerful pay bribes or use connections to help their sons get U.S. citizenship or otherwise skip the military.
Overweight men have been known to eat more, and skinny ones to fast, to win exemption. Some even get large tattoos, forbidden in the service, or tamper with X-ray photographs to avoid taking up arms.