What to do if the girls parents are threatening me not to marry

My friend was in relationship for past 5 years and they planned of getting married with the permissions of there respective parents, so they told there parents and girl's parents agree about the affair and accept the reationship but the boy's parents diidn't. Although the couple continue there reationship, thinking of that the boy is unemployed right now and there parents will agree when the boy will be employed. Now the boy is employed but after lot of discussion and attempt of making understand then also parents are not agree for the marraige. So my friend just replied the girl that he wouldn't be able to marry her because his parents are not approving it. In this case girl's family members are threating the boy that they will file a case against him for not maarying her, and forcefully make him marry her. So, i just want to know is it possible and what will be the conciquences and what should the boy should do.