On the day before President Donald Trump's next set of tariff hikes is set to materialize, a federal appeals court will grapple with the big, unanswered question underpinning the president's aggressive and unprecedented trade policies.

Salt Lake City-based Genova Pipe, a producer of chlorinated PVC and ABS pipes and fittings, and four other U.S. businesses have alleged severe economic and other harm by the so-called Liberation Day tariffs.