For decades, "freedom of navigation" has been one of the most frequently invoked phrases in discussions about the South China Sea, but the principles are interpreted so differently.

The debate is no longer simply about whether commercial shipping can move safely through one of the world's busiest waterways. The increasingly contentious question is whether the same principle should also justify expanding military operations by countries located far beyond the region.

The South China Sea needs greater respect for the rules. The United Nations Convention on the Law of the Sea (UNCLOS) provides a legal framework balancing navigational rights with the security interests of coastal states.

When military presence becomes the story

One example came in May, when the Chinese military released footage showing an illegal intrusion by Dutch forces into China's Xisha Islands.

The video showed an NH-90 helicopter taking off from the Dutch frigate De Ruyter despite receiving repeated radio warnings from a Chinese naval vessel to leave the area immediately. According to China's People's Liberation Army Southern Theater Command, the helicopter conducted multiple operational flights.

"The Xisha Islands are an inherent territory of China. The Chinese army remains on high alert and resolutely defends national territorial sovereignty and maritime rights and interests," said Jiang Bin, spokesperson for China's Ministry of National Defense.

The incident is an example of numerous military activities conducted by countries outside the region. According to the South China Sea Strategic Situation Probing Initiative (SCSPI), such operations have increased substantially in recent years.

SCSPI reported that in 2025, extra-regional countries conducted nearly 10,000 ship-days of naval presence and more than 20,000 aircraft sorties across the Western Pacific, with the United States accounting for most of those activities, followed by its allied countries.

Supporters of these deployments argue they demonstrate commitment to maintaining a free and open maritime order. Critics see a different picture: an expanding military footprint that risks adding tension to an already sensitive region.

What does UNCLOS actually say?

UNCLOS guarantees navigational rights across different maritime zones, including the right of innocent passage through territorial seas. However, those rights are not without limits. Article 25 of the Convention states that "the coastal State may take the necessary steps in its territorial sea to prevent passage which is not innocent."

The UNCLOS therefore seeks to balance navigational freedoms with the right of coastal states to safeguard their security under specified circumstances. That raises a broader question: when military aircraft and warships operate thousands of miles from their home territory, are those activities consistent with the balance envisioned by UNCLOS?

The debate has become increasingly prominent as Washington advances what it calls a "free and open" Indo-Pacific strategy while continuing to conduct "Freedom of Navigation Operations", or FONOPs.

"The United States is trying to protect not just freedom of navigation generally, but also to protect its allies and partner interests, so the Philippines in particular," said Patrick Cronin, Asia-Pacific Security Chair at the Hudson Institute.

China argues that Washington's interpretation goes beyond what UNCLOS itself provides. Chinese officials also note that the United States remains the only permanent member of the UN Security Council to have not ratified the Convention.

"The US is not a state party to the UNCLOS, and it is all the more unqualified to act as a 'judge' of the convention and dictate to other countries," China's Permanent Representative to the United Nations, Fu Cong, said in January.

Hu Bo, director of the South China Sea Strategic Situation Probing Initiative, said the dispute ultimately reflects broader political considerations.

"Because it is a hegemonic power. The fundamental reason why the United States has not ratified the UNCLOS to this day is that the United States fears that the Convention would restrict the free movement of the US military around the world," Hu said.

Rules as the foundation for stability

Since 2017, the United States has invested more than $1.5 billion in maritime law enforcement capacity across the region, supporting partner countries while continuing its Freedom of Navigation Operations.

But those operations encompass not only the passage of ships and aircraft but also military exercises, surveillance missions, flight operations, and task-force maneuvering.

The South China Sea remains one of the world's busiest and most strategically important maritime corridors, carrying a substantial share of global trade. Maintaining stability in these waters depends not only on military restraint, but also on confidence that international law is interpreted and applied consistently by all parties.

"We should follow international law like UNCLOS to help each other to understand and help to make the sea more prosperous," said Admiral Pongsak Somboon, deputy secretary general of Thailand's Maritime Enforcement Coordinating Center.

The principle of freedom of navigation is widely recognized under international law. At the same time, many argue that it should be exercised responsibly and in accordance with the broader framework established by UNCLOS.

As a landmark achievement in the development of the post-World War II international maritime legal order, UNCLOS provides the foundation for governing the world's oceans. As military activity in the South China Sea continues to increase, the importance of respecting commonly accepted rules, and the willingness of all parties to operate within them, has become more critical than ever.