(FORTUNE Magazine) – Patent law, still focused more on razorblades than cellphones, may get a dramatic update if the Supreme Court weighs in after hearing oral arguments March 29 in eBay v. MercExchange. "It's an extremely important case," says Stanford law professor Mark Lemley, who has filed a brief supporting eBay. He says that plaintiffs in patent cases can (and do) use the threat of injunctions to "hold up" technology firms and force big settlements. Case in point: the recent $612.5 million deal to end the BlackBerry siege. A ruling in eBay's favor could give judges far more flexibility in solving patent disputes--like setting a reasonable royalty--rather than simply issuing an injunction.