A high court in South Korea has acquitted a university professor of defaming people who are referred to as wartime comfort women.

The court on Friday ruled in favor of Sejong University Professor Park Yu-ha. She was found guilty in a trial seven years ago. The Supreme Court ordered a retrial last October.

The new ruling says the expressions in Park's book should be viewed as an academic argument, and cannot be considered defamation.

Park was indicted in 2015 for defaming the women in her book "Comfort Women of the Empire," published in 2013.

In the book, Park writes that the relationship between some women and the now-defunct Imperial Japanese forces was akin to that of "comrades" and that some of them voluntarily became comfort women.

A district court acquitted Park in 2017. But a high court reversed the decision later that year, and ordered her to pay a fine of 10 million won, or about 7,400 dollars at that time.

Park said she had a difficult time for over nine years and thanked her supporters.