Taft was appointed to the bench in Cincinnati at the young age of 29. The Bully Pulpit describes his most important opinion:

Will Taft’s most significant action as a superior court judge was a ruling in 1890 that addressed the balance of power between the burgeoning labor movement and industrial interests. The case involved a secondary boycott, a sanction intended to punish one business by wielding pressure against another business unrelated to the original cause of grievance. In this instance, the Bricklayers’ Union had declared a boycott against the contracting firm of Parker Brothers on grounds that the company had discriminated against its members. The union called on all suppliers of the firm’s building materials to honor the boycott. When the Moore Lime Company continued to supply Parker Brothers, the union declared it would no longer use lime supplied by Moore’s. Moore’s & Co. sued the Bricklayers’ Union for damages caused by the secondary boycott. Their suit was upheld by the lower court in Hamilton County, which awarded a verdict of $ 2,250 to the plaintiffs. When Moore’s & Co. v. Bricklayers’ Union et al. reached the superior court on appeal, Taft sustained the lower court decision, affirming that a secondary boycott against a firm with whom there was no dispute was illegal. His decision was upheld by the Ohio Supreme Court. Decades later, it remained a leading case on the law of secondary boycotts.

While his decision worked to limit the power of organized labor, Taft revealed a sympathy for the rights of workers that his more conservative colleagues did not share. He was careful to underscore the union’s prerogative in withdrawing its members from Parker Brothers; when the union turned on an unrelated company, however, it had exceeded its legal bounds. Though Taft refused to condone the union’s action in this case, he argued strongly for a laborer’s “right to work for such wages as he chooses, and to get as high a rate as he can.” He maintained that an individual “may lawfully notify his employers of his objection and refuse to work,” and concluded that “what one workman may do  .  .  . many may combine to do.”

I found a report of the opinion here.