Marley's heirs filed suit in January 2008, alleging Nevada-based Avela and its owner Leo Valencia intentionally interfered with the family's businesses, Fifty-Six Hope Road Music Ltd. and Zion Rootswear, which were formed by the singer's widow Rita and nine of his 11 children.
According to court filings, Avela executives first licenced Marley's identity in 1986 and then in 1999, and granted Zion Rootswear bosses the exclusive worldwide license to design, manufacture and sell T-shirts bearing Marley's image. But Valencia was accused of selling his own T-shirts and other products featuring Marley's likeness across America.
A federal jury ruled in favour of the star's family Friday and US District Judge Philip Pro ordered Valencia to pay the Marleys $300,000 in damages, reports contactmusic.com.
Judge Pro is expected to award further damages for his loss due to unfair competition.
Following the ruling, the icon's son Rohan Marley said: '(The verdict) affirms what we've been saying all along. We are the rightful owners of all rights to our father's identity and persona - not because we inherited it, but because we had to buy back those rights many years ago and have taken great care to protect his legacy, identity and persona since his passing almost 30 years ago.'
The defendants' lawyers are now planning to appeal the ruling.
Marley died of cancer in 1981, aged 36.