In the lawsuit, Lone Star demanded Hana Financial pay $1.4 billion in compensation.
Lone Star bought a 50.5 percent stake in Korea Exchange Bank for 1.4 trillion won ($1.18 billion) in 2003 before selling a 51.02 percent stake in the Korean lender to Hana Financial for 2.02 trillion won in 2012.
The international court informed Hana Financial of the ruling, the company said.
In 2012, Lone Star also filed an investor-state dispute arbitration claim against the South Korean government for alleged losses related to its investment in Korea Exchange Bank.
The World Bank unit for investor-state dispute arbitration is expected to issue a ruling over the case later this year.
By Ram Garikipati and newswires (firstname.lastname@example.org)