The German Bundesliga side have reportedly signed the 21-year old for 2million for K-League club Jeju United but Swiss outfit Young Boys claim they had a deal with the talented midfielder although an agreement with Jeju had not been confirmed.
FIFA are set to investigate the situation but Wolfsburg director Dieter Hoeness says his club has done nothing wrong.
"We have done things as we should have," said Hoeness. "The player will be joining us."
Koo's services have been sought after he was the Golden Boot winner at last month's Asian Cup in Qatar, scoring five times for the Tageuk Warriors who finished in third place behind winners Japan and runners-up Australia.