EXCLUSIVE
Jason Patric just won a 2-year legal battle against his baby mama -- a judge just declared he is the legal father of 4-year-old Gus ... TMZ has learned
Jason had a baby with ex-GF Danielle Schreiber, and after breaking up, going back and breaking up again, she fought hard against his bid to become the legal father, citing a quirky law.
According to the law ... if a man donates sperm to a woman to whom he is not married and a doctor facilitates the insemination ... the man has NO claim of custody or parental rights.
The trial judge ruled against Jason , he appealed and the appellate court said the trial judge was off base and sent it back for another hearing.
The second time was a charm for Jason. We've learned the trial judge just issued a sealed, 45-page opinion, concluding Jason is the legal father.
The judge ordered Jason, Danielle and their lawyers to try and hash out a custody, visitation and support agreement, but if they can't the judge will make the decisions.
This case became a rallying cry for father's rights -- enormous victory for Jason.
