Alienation of Affections as Complicity
In the discussion of the Kyrsten Sinema alienation of affections case, several commenters took roughly the following view: Spouses have promised fidelity to each other, and if they break those promises, they are at fault towards the other spouse. But one spouse's lover hasn't made any promises to the other spouse. The lover therefore can't be said to be at fault.
I don't think that view is right, and I don't think it fits the norm for how our legal system treats analogous scenarios. I think that on balance the abolition of the alienation of affections tort (which has happened in 45 states) is a good idea. But not for the reason that "the lover isn't at fault, only the spouses are."
Rather, alienation of affections is analogous to complicity liability. If Alan commits an intentional wrong against Betty, either a crime or a tort, and Cathy encourages Alan to do that, Cathy is generally liable. The term sometimes used for this is "solicitation," though sometimes it's seen as a form of aiding and abetting.
If Cathy helps Alan in committing the wrong, or participates in committing it, Cathy is likewise liable for aiding and abetting or conspiracy. (Both those concepts apply to civil liability as well as criminal liability.)
Perhaps most analogously to alienation of affections, if Alan breaches his contract with Betty, and Cathy encouraged him to breach it, she will in many situations be liable for intentional interference with contract. Likewise if Alan breached a fiduciary duty to Betty, and Cathy encouraged that breach.
Now there can be complications here. Among other things, complicity liability will often apply only if Cathy has the purpose of bringing about Alan's misbehavior, or at least knows that Alan is misbehaving. Negligently providing assistance is enough in some cases (see, e.g., negligent entrustment of cars or weapons), but usually not enough. But in many alienation of affections cases, the defendant knew that the defendant's lover was married.
And I think that on balance this sort of complicity liability makes sense in most situations. Knowingly helping someone else commit a wrong against a third party, and especially urging that person to commit the wrong, is itself a wrong against the third party. But whether or not you agree with that, that's the dominant view in our legal system.
The intentional interference with contract example also responds to the argument that "spouses don't own each other, so a third party can't 'steal' a spouse from the other spouse." Contracting parties also don't own each other: If Alan promises to sing in Betty's opera house for a year, that doesn't mean that Alan is Betty's property. But if Cathy lures Alan away to instead sing in her opera house, especially knowing of Alan's binding contract with Betty, then she is liable—not for stealing Alan as if he were property, but for inducing his breach of the contract that he voluntarily entered into. Likewise, an alienation of affections claim doesn't rely on claims of ownership any more than does the intentional interference claim.
As I said, I think there are good reasons why the alienation of affections tort has been abolished in the great majority of states. I'll likely write a bit more about those reasons in a later post. But I think the reasons are largely functional and pragmatic, rather than conceptual. The inability to sue those who aid in the wrong of adultery is actually something of a departure from the conceptual framework of civil and criminal liability.