In the wake of Washington’s second “freedom of navigation” operation near Beijing’s man-made islets in the South China Sea, an often overlooked fact remains: The set of laws governing global maritime behavior that the U.S. has been touting has never been ratified by the Senate.

The U.S., which conducted the operation Saturday in waters 12 nautical miles (22 km) from Triton Island in the Spratly archipelago, has repeatedly urged its Asian rival to adhere to international law to solve disputes.

But analysts and experts say Washington risks creating a credibility gap by citing the very measure — the United Nations Convention on Law of the Sea (UNCLOS) — it has repeatedly failed to ratify.

“While U.S. policy is based on scrupulously observing UNCLOS provisions, failure to ratify denies Washington the moral high ground,” said Euan Graham, director of the International Security Program at the Lowy Institute in Sydney. He said the issue has been a constant embarrassment to U.S. officials and politicians traveling throughout the Asia-Pacific region.

President Bill Clinton signed the agreement in 1994. It has since languished in Congress, with attempts to pass it blocked by conservatives who question the value of an agreement that they say adds nothing to conventions long established.

While the United States does not take a position on maritime territorial disputes such as those in the South China Sea, President Barack Obama has repeatedly urged the peaceful resolution of such rows, including the use of international arbitration under UNCLOS.

But for years, critics say, U.S. failure to ratify the treaty has been a weak spot in the armor of a dynamic American foreign policy — especially in the Asia-Pacific region, where Washington has sought to refocus its energy with its so-called rebalance.

Discussions on the law of the sea were concluded in 1982 and came into force in 1994, the same year the U.S. signed it. This eventual inking of the pact came after negotiations on a number of concerns cited by Washington were addressed, namely issues concerning seabed mining.

Clinton had even asked for and received revisions and special powers not given other treaty signatories, including what amounted to veto power over anything to Washington’s disliking.

According to John B. Bellinger III, a former legal adviser for the State Department under President George W. Bush, both the Bush and Obama administrations have pushed for passage of the treaty.

Officials in the State and Defense Departments and the U.S. military are especially concerned that a failure to ratify UNCLOS undercuts Washington’s ability to complain when it believes Beijing is violating or misinterpreting the treaty, Bellinger said. Executive branch officials have made this argument repeatedly to lawmakers.

Still, the deal has foundered in the U.S. Senate, where treaties need a two-thirds vote to be confirmed. The last attempt at passage, in 2012, fell flat when a group of 34 mainly Republican senators blocked ratification.

Surprisingly, some say, this opposition has come in the face of calls to pass the legislation from both big business and the military — both typically key bastions of Republican support.

“It has indeed been surprising that many Republican senators oppose U.S. ratification of the UNCLOS despite strong support by the U.S. military and the U.S. business community, including oil and gas, telecommunications, and shipping,” Bellinger said.

These senators, he added, tend to be influenced by the views of conservative advocacy groups that are suspicious of multilateral treaties and U.N. institutions, which the groups believe may threaten U.S. sovereignty.

Critics of UNCLOS, Bellinger said, “believe that the U.S. can continue to rely on navigational and maritime rights accepted in customary international law. Indeed, they criticize UNCLOS because it has not constrained China’s excessive maritime claims. Critics … see international law as ineffective.”

Beijing ratified UNCLOS in 1996, and top Chinese diplomats have repeatedly emphasized the nation’s commitment to the treaty, though China has questioned its jurisdiction in the South China Sea dispute.

Beijing has simultaneously rebuked American failure to conclude the treaty.

In April, Chinese Ambassador to the U.S. Cui Tiankai touted China’s position as “one of the first countries to join and ratify UNCLOS,” while also taking a subtle jab at Washington by noting that Beijing “welcomes more countries, including the United States, to join.”

One group that has lobbied hard to prevent U.S. ascension to UNCLOS has been the conservative Heritage Foundation think tank.

In an April 2014 report entitled “A National Strategy for the South China Sea,” the think tank argued that China is unlikely to be swayed by U.S. ratification of a treaty that Beijing “regularly violates or simply ignores.”

“The customary international law of the sea — which includes the principles of freedom of the seas, ‘innocent passage’ through territorial waters, and passage rights through international straits and archipelagoes — existed long before UNCLOS was adopted in 1982,” the study noted. “While not a party to UNCLOS, the United States — unlike China — actually honors the convention’s provisions,” it said.

But some law experts believe that an overreliance on customary international law could cause trouble for the United States in the future.

“Customary international law can change, whereas the treaty rights are clear,” said Bellinger, who has testified before the Senate several times to urge approval of UNCLOS.

Still, while the Senate’s failure to ratify the treaty clearly deprives the U.S. of some authority to complain if other countries violate it, Washington still retains a powerful voice on maritime issues.

The U.S. can continue to argue that most of the key provisions of UNCLOS applicable to the South China Sea disputes, including maritime entitlements and navigational freedoms, are customary international law that is binding — regardless of whether a country has treaty obligations under UNCLOS.

“In practical terms, it is doubtful that U.S. ratification would have any significant effect on Beijing’s position,” said Alex Calvo, a visiting professor at Nagoya University.

“This does not mean that ratification may not have other benefits, but it would be wishful thinking to imagine that the PRC will become more flexible concerning the South China Sea simply because Washington ratifies UNCLOS,” he said, referring to China by the initials for its formal name, the People’s Republic of China.

James Kraska, research director at the Stockton Center for the Study of International Law at the U.S. Naval War College, argues that the treaty could eventually become a valuable tool in helping solve the disputes in the South China Sea and elsewhere.

“Like all of international law, UNCLOS cannot be viewed in isolation of international politics,” said Kraska. “Although China says now that it will not be bound by compulsory dispute resolution in the South China Sea, I believe that over time Beijing may quietly start to cede on some of the issues because of the authority and power of the law.”

This, Kraska said, is because China has increasingly found itself isolated on maritime issues, especially as a decision looms on territorial claims in the South China Sea by a tribunal at the Permanent Court of Arbitration.

China has refused to participate in the case, saying it has “no legal grounds” under UNCLOS. It is widely expected to reject any outcome it does not agree with.

“If the tribunal issues an award that repudiates China, Beijing will have to contend with it — it will not just go away,” Kraska said. “The importance of the tribunal in this regard is to demonstrate to China that international law and UNCLOS have real consequences for Chinese foreign relations.

“The pressure will grow on China to think about how it can bring its claims into compliance with UNCLOS, even if the process takes decades,” he said.