The Black Cats issued a statement on Friday afternoon any denying wrongdoing in regard to the matter. Ji made four Barclays Premier League appearances without the correct international clearance, plus one in the Capital One Cup. Their opponents in that competition, MK Dons, also released a statement on Friday saying they would not pursue the matter further.
Sunderland were fined in December last year after they alerted league officials to the fact that they did not have international clearance for Ji, although the news has only emerged in the last 24 hours.
A club spokesperson said on Friday: "The issue of Ji Dong-won was explained in detail to (Friday's) Premier League shareholders meeting and no issues were raised by any club.
"Sunderland AFC confirmed that they had complied with all the procedures and the Premier League stated that the player was duly registered on the extranet system and in all other Premier League mechanisms.
"The club has never accepted any wrongdoing, but did acknowledge that a technical fault occurred and as such, were fined by the Premier League accordingly in December.
"The matter is now closed."
MK Dons said in a statement: "The club sought clarification from the Football League regarding the allegations and the League confirmed that they only became aware of the situation in late November.
"The club acknowledges that the Football League board dealt with the situation as they saw fit and will not be pursuing the matter further."