Adultery legalizes In South Korea - Park Han-Chul

The Presiding justice in the South Korean Constitutional Court  Park Han-Chul while sticking the law yesterday the 25th of February said though the act of adultery is bad, that the country has not power to interfere into people's private affairs. He quotes

"Even if adultery should be condemned as immoral, state power should not intervene in individuals’ private lives,” said presiding justice Park Han-Chul.

In the last six years, close to 5,500 people have been formerly arraigned on adultery charges including nearly 900 in 2014. In 2004, 216 people were jailed for adultery but the numbers dropped to 42 in 2008 and from 2008 till date, only 22 people had been sentenced to jail.

Now, married people in South Korea can have sex with other people and not face any penalty. I kinda support this. Why jail someone for adultery?