SEOUL (Reuters) - South Korea's highest court struck down a decades-old law banning adultery, a statute that critics said is anachronistic and infringes on personal freedom, sending shares in the country's biggest condom maker surging.

The law had been enacted in 1953 to protect women in a male-dominated society where divorce was rare and had made marital infidelity punishable by 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 under the constitution," said Seo Ki-seok, a Constitutional Court justice, reading an opinion representing five justices.

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

Shares in Unidus Corp, which makes latex products including condoms, soared to the 15 percent daily limit gain after the ruling.

Critics have said the law against adultery is outdated in a society where rapid modernization has frequently clashed with traditionally conservative values.

In 2008, the court had upheld the law, citing the society's legal perception that adultery is damaging to social order.

Several thousand spouses file criminal adultery complaints each year in South Korea, although it is rare for someone to be jailed. According to prosecutors, no one was put behind bars last year although 892 were indicted on adultery charges.

(Reporting by Ju-min Park; Editing by Tony Munroe)