The right to divorce? Anyone has the right to divorce. You don’t need a halachic reason
Absolutely, completely and utterly incorrect. In order to unilaterally insist upon a divorce one most certainly does need a reason Halacha deems justifiable to mandate the other spouse give/accept the divorce. If both spouses mutually desire to divorce, no further reason is needed and they can do so. But if one spouse wishes to divorce whereas the other spouse wishes the marriage to continue, if the spouse desiring the divorce does not have a provable “cause” that is one of the few that Halacha deems justification to mandate that the spouse give/accept a Get, then the other spouse has the right to decline and refuse to give/accept a Get and Beis Din is halachicly mandated to accept the declining spouse’s insistence that the marriage not terminate in divorce.
The above is m’doraisa when it is the husband who doesn’t want to divorce. The Shulchan Aruch states that Beis Din can only mandate he give a divorce if one of the specific reasons the Gemorah lists as allowing a wife to force her husband to divorce her is applicable and proven. There are only a handful of reasons. (Certain physical deformities, physical violence, etc.) The Shulchan Aruch even says that if she claims he’s physically violent and he denies it (saying she’s claiming that only to force him to unwillingly divorce her), Beis Din needs to place an agent in their marital home to witness the veracity of the claim before they can accept her word. (And even that can only be done after they warned him to stop and she claims he’s continuing post-warning from B”D.)
If it is the husband who wants to divorce but the wife doesn’t want to divorce, she has the right to veto his ability to divorce her based upon that right given to her (which mimicks his similar m’doraisa right in this regard) based on Cherem D’Rabbeinu Gershom. If he’s Ashkenazic. If he’s not Ashkenazic then she doesn’t necessarily even have this right to stop him from divorcing her.
Importantly, note that Rabbeinu Gershom extended the right of one spouse to veto the other spouse’s request to divorce where that veto right didn’t exist pre-R”G. This point further underlines my point that a spouse has a veto right when their spouse requested a divorce. Rabbeinu Gershom even extended this veto (to the wife.)
although their are halchachic reasons when a divorce is commanded.
Indeed their are. Also worthy of noting is that Halacha has reasons when a requested divorce is automatically denied. For example, the Shulchan Aruch states that if the desire for divorce is because she wants to marry another specific person, her request is denied.
Upon hearing everything the Rav decides divorce is the best road. Don’t tell me that the couple does not have the right to divorce.
If they mutually agree with him, sure they have the right. But if one doesn’t agree, and there’s no halachic cause, then that right does not exist.