WASHINGTON — Landowners who say a North Carolina electronics plant poisoned their drinking water missed a filing deadline, the Supreme Court ruled on Monday.

The decision, in a 7-to-2 vote, is likely to affect similar suits from the families of thousands of former Marines over what they say was toxic pollution at Camp Lejeune, also in North Carolina.

The case decided on Monday concerned a 1980 federal law that made it easier to sue over environmental contamination, which can be hard to discover and may cause symptoms only decades later. The law said state statutes of limitations do not begin to run until plaintiffs learn of, or should have discovered, the harm in question.

The plaintiffs in Monday’s case said their drinking water had been contaminated between 1959 and 1985 by a plant in Asheville, N.C., run by CTS Corporation. They sued in 2011, after a 2009 report from the Environmental Protection Agency.