A judge ordered Google to make it easier for developers of mobile app stores to compete on phones and tablets that use the company’s Android software, a blow to the search giant as it navigates numerous legal threats.

The injunction by U.S. District Judge James Donato in San Francisco outlined the changes Google must undertake to open up its lucrative app store, Play, to greater competition, including making Android apps available from rival sources.

Judge James Donato, who presided over the Epic vs. Google lawsuit that declared Google to be operating an illegal monopoly with its Google Play Store on Android last year, issued a final ruling on Monday requiring the company's mobile operating system to open up to third-party app stores for three years.