This unanimous opinion in Fox v. Vice from Justice Kagan limits the scope of recoverable attorney’s fees  to those that are not incurred but for frivolous claims.

Federal law authorizes a court to award a reasonable attorney’s fee to the prevailing party in certain civil rights cases. See 42 U. S. C. §1988. We have held that a defen-dant may receive such an award if the plaintiff’s suit isfrivolous. In this case, the plaintiff asserted both frivolous and non-frivolous claims. We hold today that a court may grant reasonable fees to the defendant in this circum-stance, but only for costs that the defendant would not have incurred but for the frivolous claims. A trial court has wide discretion in applying this standard. But here we must vacate the judgment below because the court used a different and incorrect standard in awarding fees.

Kagan’s prose is lovely:

These standards would be easy to apply if life were like the movies, but that is usually not the case. In Hollywood,litigation most often concludes with a dramatic verdict that leaves one party fully triumphant and the other utterly prostrate. The court in such a case would know exactly how to award fees (even if that anti-climactic sceneis generally left on the cutting-room floor). But in the real world, litigation is more complex, involving multiple claims for relief that implicate a mix of legal theories andhave different merits. Some claims succeed; others fail. Some charges are frivolous; others (even if not ultimately successful) have a reasonable basis. In short, litigation is messy, and courts must deal with this untidiness inawarding fees.

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The question then becomes one of allocation: In a law-suit involving a mix of frivolous and non-frivolous claims, what work may the defendant receive fees for? Vice con-cedes, as he must, that a defendant may not obtain com-pensation for work unrelated to a frivolous claim. Brief for Respondents 42, n. 13. Similarly, we think Fox would have to concede (once he has lost the argument that the presence of any non-frivolous claim precludes a fee award) that the defendant may receive reasonable fees for work related exclusively to a frivolous claim. The question indispute concerns work that helps defend against non-frivolous and frivolous claims alike—for example, a depo-sition eliciting facts relevant to both allegations.

Kagan phrases this question as a “but-for” test.

That congressional policy points to a different and more meaningful standard: Section 1988 allows a defendant to recover reasonable attorney’s fees incurred because of, but only because of, a frivolous claim. Or what is the same thing stated as a but-for test: Section 1988 permits thedefendant to receive only the portion of his fees that hewould not have paid but for the frivolous claim. Recall that the relevant purpose of §1988 is to relieve defendantsof the burdens associated with fending off frivolous litiga-tion. See supra, at 5–6. So if a frivolous claim occasioned the attorney’s fees at issue, a court may decide that thedefendant should not have to pay them. But if the defen-dant would have incurred those fees anyway, to defend against non-frivolous claims, then a court has no basis for transferring the expense to the plaintiff.

Kagan, in reliance on the “American rule,” would avoid construing the fee-shiting statute to “furnish windfalls to some defendants, making them betteroff because they were subject to a suit including frivolous claims.”

So two defendants (callthem Vice and Rice) could face identical non-frivolousallegations, but because Vice also confronted a frivolous claim, he might end by paying less than Rice to his attor-neys. The chance assertion—for Vice, the downright luckyassertion—of the frivolous claim could relieve him not onlyof the incremental costs of that claim but also of costs that he, like Rice, would have had to pay in its absence