Per FanNation.com,
"Song submitted a petition to the Navy after he was drafted in an effort to be allowed to pursue a professional baseball career, but there has been no resolution as of yet. Thus, Song continues to serve his active duty time.
However, when/if he is allowed to return to baseball, the Phillies will have to follow normal Rule 5 policy, meaning that Song will have to remain on their active roster for an entire year in order for Philadelphia to retain control over the player."