Ultimately, that was the reason for the judge's decision. Owners of patents for technology essential to mobile standards are required to offer FRAND (Fair, Reasonable, And Non-Discriminatory) licensing terms to any and all manufacturers.
According to AFP, a panel of judges found that Samsung is "obliged to grant a licence to Apple according to the terms of FRAND for the patents."
Ultimately, this is the same decision expected in other jurisdictions where Samsung has filed similar lawsuits. In fact, lawsuits of this type are exactly the reason FRAND licensing exists.
Without such terms it would be impossible to develop industry standards for fear patent holders would hold gain unreasonable control over entire industries.