SEOUL - South Korea's highest court on Thursday struck down as unconstitutional a decades-old law banning adultery, triggering a surge in shares of condom makers and morning-after pills.

The 1953 law aimed to protect women in a male-dominated society where divorce was rare, by making marital infidelity punishable with jail.

"The law is unconstitutional as it infringes people's right to make their own decisions on sex and secrecy and freedom of their private life, violating the principle banning excessive enforcement," said Seo Ki-seok, a Constitutional Court judge, reading an opinion on behalf of five judges.

Seven members of the nine-judge panel deemed the law to be unconstitutional.

After the ruling, shares in Unidus Corp, which makes latex products, including condoms, soared to the 15% daily limit gain.

Hyundai Pharmaceutical Co Ltd, a maker of morning-after birth control pills and pregnancy tests, ended up 9.7% after the court decision, recovering earlier losses.

Critics have said the law against adultery is outdated in a society where rapid modernization has often clashed with traditional values.

In 2008, the court had upheld the law, citing South Korean society's legal perception that adultery damages social order.

Several thousand spouses file criminal adultery complaints each year in South Korea, although jailings are rare. Prosecutors say no one was put behind bars last year, despite 892 indictments on adultery charges