The Ohio Supreme Court yesterday struck down a law that had sharply curtailed the ability of individuals to sue for damages, concluding that the state legislature violated the separation-of-powers doctrine when it passed the provision two years ago.

The 4 to 3 decision was viewed as a bellwether by legal experts and the strongest sign yet that trial lawyers and consumer advocates are winning a decade-old fight to roll back "tort reform" laws designed to limit big jury awards and reduce the number of personal-injury lawsuits.

"The Ohio decision means that state tort reform faces major hurdles that are going to be extraordinarily difficult to overcome," said Victor Schwartz, general counsel of the American Tort Reform Association (ATRA), a group backed by business interests and pushing for liability restrictions.

For lawyers, these state-level victories are crucial because the effort to restrict personal-injury and product-liability lawsuits has all but stalled in Washington. Congress is too divided on the topic to pass anything but modest, targeted bills, and President Clinton, a longtime ally of trial lawyers, has promised to veto any broad tort-reform measures.

Meanwhile, states have been quietly overturning their own tort-reform laws, many of them passed by Republican-led legislatures in the past two decades. Through the 1980s and 1990s, corporations successfully lobbied state capitals for relief from what they called "jackpot justice," multimillion-dollar awards occasionally bestowed on plaintiffs by outraged juries.

Business interests have long decried such verdicts, arguing they are typically based on flimsy claims and are reached by jurors swayed by emotions more than facts. In response, dozens of states passed laws that scaled back the chances of a plaintiff winning huge sums in personal-injury lawsuits.

But in the past few years, trial lawyers have been challenging these laws with growing success. Top courts in Kentucky, New Hampshire, Illinois and Indiana have chipped away or scrapped tort-reform laws. In some states, the laws have withstood judicial scrutiny; the Virginia Supreme Court, for instance, affirmed a rule placing limits on medical malpractice awards. But ATRA estimates that roughly 90 decisions in state and local trial courts across the country have taken aim at laws that limit legal liability.

In Ohio, the fight became a high-profile showdown because in 1997 the state passed the country's most ambitious tort-reform law. The measure placed limits on noneconomic damages and wrongful-death actions, raised standards of proof, and required would-be litigants to obtain an affidavit from a doctor affirming their injuries.

But a slim majority on Ohio's Supreme Court ruled that the legislature had overstepped itself. Judges, not lawmakers, are responsible for making rules about access to the legal system, the judges said. Ceding that power would make the courts a "coconspirator in the abdication of fundamental individual rights and liberties contained in our Constitution," the judges wrote. The opinion also took the lawmakers to task for including elements in the 1997 law that had already been declared unconstitutional.

The ruling has no binding effect outside of Ohio, but legal experts said it would influence the course of debate in other states. If the law had passed judicial muster, they said, it could have inspired other legislatures to pass identical statutes. Attorneys for hospitals, insurers, manufacturers and a handful of corporations submitted 17 legal briefs, urging the judges to uphold the law.

Unlike other challenges to tort laws, this one did not stem from a personal-injury case. Instead, the Ohio Academy of Trial Lawyers filed suit on unusual grounds--that the law was so Draconian it forced lawyers to abandon personal-injury law, causing a precipitous drop in the organization's membership.

"What we're seeing is that these statutes that attempt to cover the waterfront of tort reform don't fly," said Richard Peck, the lawyer who argued the case for the Ohio academy.