MARSHFIELD, Vt.  When Diana Levine starts talking about her rock ’n’ roll days, she plays a little air guitar, mimicking the way she used to handle her electric bass in bands like the Re-Bops and Duke and the Detours. But Ms. Levine is missing much of her right arm, which was amputated below the elbow after a medical disaster.

She sits at her kitchen table, strumming an imaginary guitar with a phantom hand.

In November, the Supreme Court will hear arguments about whether Ms. Levine may keep more than $6 million that a Vermont jury ordered Wyeth, a pharmaceutical company, to pay her for failing to warn her adequately about the risks of one of its drugs. The case, the latest in a brisk parade of similar ones, will help define the contours of a signature project of the Roberts court.

In legal jargon, the cases concern “pre-emption,” a doctrine that can bar injured consumers like Ms. Levine from suing in state court when the products that hurt them had met federal standards. The issue is less boring and more consequential than it sounds, and Ms. Levine’s case is shaping up to be the most important business case of the term.

“Federal pre-emption is the fiercest battle in products liability law today,” said Catherine M. Sharkey, a law professor at New York University. “The court clearly recognizes this, as it has agreed to hear so many cases and seems eager to give clarity to what has been, to date, an undisputably muddled area of law.”