The U.S. Supreme Court on Monday left in place a lower court ruling that allowed a New Jersey woman to sue a tuna-fish producer over the mercury poisoning she allegedly suffered after her diet consisted almost exclusively of canned tuna for five years.

The woman, Deborah Fellner, said Tri-Union Seafoods LLC, the maker of Chicken of the Sea brand tuna, failed to warn her of the risks of consuming tuna fish.

Tri-Union said U.S. Food and Drug Administration regulations prevented it from placing a mercury warning label on its products. The company said that Fellner's suit should be thrown out because it conflicted with the FDA's regulatory regime.

A federal trial judge had tossed Fellner's lawsuit, but an appeals court in Philadelphia reinstated it, saying the FDA had taken no regulatory action that preempted her legal claims.

The Supreme Court rejected Tri-Union's request that it review the case. Instead, the justices let the lower court ruling stand without comment.

Tri-Union argued that the appeals court ruling put it in the untenable position of facing legal liability under state law for not including a warning label that would have rendered its products misbranded under federal law.

Among other things, the company pointed to a 2005 letter the FDA sent former California Attorney General Bill Lockyer, who was attempting to sue Tri-Union for not placing a warning label on its products. The FDA told Lockyer that such warning labels were preempted by federal law. The agency said it had analyzed the issue for several years and decided not to require mercury warning labels on seafood products.

Fellner said the FDA's actions on mercury in seafood were informal in nature and not strong enough to preempt her legal claims.

In other Supreme Court action Monday, the justices refused to review a federal appeals court ruling that allowed shareholders to bring a class action securities-fraud lawsuit against Gilead Sciences Inc. (GILD) for allegedly concealing a fraud related to the company's key HIV drug Viread in 2003.

The plaintiffs alleged that demand for the drug was artificially inflated because Gilead was secretly and illegally marketing the drug for uses not approved by the FDA. Gilead said the plaintiffs' could not show that any decrease in the company's stock price was connected to the alleged fraud.

 
-By Brent Kendall, Dow Jones Newswires; 202-862-9222; brent.kendall@dowjones.com