The civil suit comes as nuclear arms are increasingly being linked to other pressing international issues, such as the prosecution of war crimes and crimes against humanity and the effort to combat climate change.

Image A doctor examined a resident exposed to radiation. Credit... Atomic Energy Commission

Meeting in Vienna this month, humanitarian law experts from 160 nations reiterated that the threat from nuclear arms or other weapons of mass destruction was incompatible with human rights principles. Scientists have stepped up warnings that using even a small percentage of the world’s nuclear arsenal would radically change the atmosphere and could cause drops in temperatures and large-scale crop failures.

More than a dozen international law experts have donated time to assist the tiny Marshall Islands, a string of atolls with 70,000 inhabitants. Rick Wayman, the director of programs at the California-based Nuclear Age Peace Foundation, said that a coalition of 55 international peace and other activist groups were backing the initiative.

One of the key questions that the court’s 15-judge bench is likely to consider is whether modernizing existing arsenals amounts to a new arms race forbidden under existing agreements. The United States and Russia, which control most of the world’s nuclear weapons, have cut old stockpiles and agreed to further reductions under a 2010 bilateral accord. But both countries, along with China, are now engaged in major upgrading of their missile systems. Pakistan and India have been in an arms race for more than 15 years.

The court is also being asked to establish a new disarmament calendar. The Marshall Islands’ suit asks that the nuclear powers begin negotiations on a disarmament treaty one year after the court’s ruling. But, as John Burroughs, director of the New York-based Lawyers Committee on Nuclear Policy, noted: “There have never even been any multilateral negotiations to eliminate nuclear weapons since the 1968 nonproliferation treaty.”

One big question is whether the judges would go beyond an opinion they issued in 1996. Asked to advise the United Nations General Assembly, the judges said unanimously that the obligation existed “to pursue in good faith and bring to a conclusion” negotiations leading to nuclear disarmament. Experts say the bench may be more divided this time.

It is far from clear how the judges will vote. Although the bench is meant to be independent, six of the 15 judges come from nuclear powers — the five original nations plus India. Heikelina Verrijn Stuart, co-author of “The Building of Peace,” a comprehensive history of the International Court of Justice, said that politics have usually trumped international law and that in the majority of the court’s cases, judges have ruled in favor of their country of origin. “Most states simply do not accept a higher legal authority,” she said, adding, “however there is no reason to suggest that the I.C.J. judges are in any way instrumental to the politics of their country of origin.”