The Law of the Sea Treaty (LOST)—signed by the U.S. in 1994 but never ratified by the Senate—is showing some signs of life on Capitol Hill, even as new circumstances make it less attractive than ever. With China emerging as a major power, ratifying the treaty now would encourage Sino-American strife, constrain U.S. naval activities, and do nothing to resolve China’s expansive maritime territorial claims.

At issue is China’s intensified effort to keep America’s military out of its “Exclusive Economic Zone,” a LOST invention that affords coastal states control over economic activity in areas beyond their sovereign, 12-mile territorial seas out to 200 miles. Properly read, LOST recognizes exclusive economic zones as international waters, but China is exploiting the treaty’s ambiguities to declare “no go” zones in regions where centuries of state practice clearly permit unrestricted maritime activity.

Take the issues of intelligence, surveillance and reconnaissance, both by air and sea. LOST is silent on these subjects in the exclusive zones, so China claims it can regulate (meaning effectively prohibit) all such activity. Beijing also brazenly claims—exploiting Western green sensibilities—that U.S. naval vessels pollute China’s exclusive zone, pollution being an activity the treaty permits coastal states to regulate out to 24 miles.

China wants to deny American access to its nearby waters so it can have its way with its neighbors. Beijing is building a network of “anti-access” and “area denial” weapons such as integrated air defenses, submarines, land-based ballistic and cruise missiles, and cyber and anti-satellite systems designed to make it exceedingly hazardous for American ships and aircraft to traverse China’s exclusive zone or peripheral seas.

If the Senate ratifies the treaty, we would become subject to its dispute-resolution mechanisms and ambiguities. Right now, since we are the world’s major naval power, our conduct dominates state practice and hence customary international law—to our decided advantage.

This dispute is not really about law. China simply does not want the U.S. military to gather intelligence near its shores. And other nations quietly support China’s position, including Russia, Iran, Brazil and India. Given China’s incessant incursions into the exclusive zones of other Asian nations such as Vietnam, the Philippines and Japan, these states may seek to restrict international maritime activities in their exclusive zones as well, further complicating U.S. efforts.

All Washington wants is to continue doing what it has been doing since it became a maritime power: use its Navy to enhance international peace and security, deter conflict, reassure allies, and collect intelligence. LOST undercuts these strategic imperatives, and that is why it has always been a bad idea for the U.S.—a formula for endless legal maneuvering and the submission of conflicting claims to the treaty’s international tribunal, where our prospects are uncertain at best.

One hopes India and Japan will stop reflexively supporting LOST. They have significant alternatives to check China’s growing power, including closer cooperation with the United States. The treaty is not an answer—it is only a beguiling, flawed escape hatch from the hard work America and others must do to meet China’s challenge.

That hard work must include properly funding and equipping the Navy and exercising it in China’s exclusive zones, including especially on intelligence missions, based on long-established state practice. Together with diplomacy to prevent nascent conflicts from escalating, these steps will reassure allies of full U.S. support in resolving disputes with China.

Mr. Bolton served as U.S. ambassador to the United Nations from 2005 to 2006. Mr. Blumenthal was a senior country director for China and Taiwan in the Office of the U.S. Secretary of Defense. Both are fellows at the American Enterprise Institute.