Korea's Constitutional Court ruled on Thursday that the Information Communication Law which requires verification of identities in order to post comments online was unconstitutional.
The policy was implemented in 2007 to curb malicious comments online, and the court had "unanimously decided" that the law violated people's freedom of speech, The Korea Times reported.
It also noted that the system did not seem to have benefitted the public as despite being enforced, the number of illegal or malicious postings online did not decrease, the court said in its verdict. Instead, users had moved to foreign Web sites and the system became discriminatory against domestic operators.
Foreigners, who did not have a resident registration number, were also prevented from expressing their opinions online, the verdict added.
Until the law was declared unconstitutional, South Korean Web sites with more than 100,000 visitors a day had required users to authenticate their identities by entering their resident ID numbers.
Google last year had refused to comply with South Korea's real-name law, stating that "freedom of expression is the most important value to uphold on the Internet".
Elsewhere, China's government also decreed microblog users in certain parts of China such as Guangdong and Beijing must also register their real names with their microblog accounts.