In compliance with South Korea's new "Game Industry Promotion Act," Sony is temporarily suspending the PlayStation Store and "related services" in the region on June 29.
The new law, which will take effect on July 1, stipulates that individuals under 18 (minors, essentially) can't be asked to give their real name as a part of any account authentication process. Since the PlayStation Store goes by this method of authentication, Sony Computer Entertainment is completely stopping the service in Korea until they can come up with a viable alternative.
As it stands, they don't have enough time to figure out and implement a new system before July 1. While SCEK hopes to bring the store and other affected services back online some time this year, they're not exactly sure how long the entire downtime will last. Until then, purchase of new content, download, and online game registration won't be possible for users in the region.