Hawaii isn’t protected by NATO. Some senators are trying to change that.

A bipartisan group of senators — led by Sens. Brian Schatz (D-Hawaii) and Eric Schmitt (R-Mo.) — made a renewed attempt this week to secure protections for Hawaii. They wrote in a letter to Secretary of State Antony Blinken on Wednesday that action was necessary to address “the deep concerns about deterring an adversary’s attack or treating residents as equals to those in the other 49 states.”

The senators added that “the gravity of the Indo-Pacific threat environment requires that we do more” amid rising concerns about an increasingly aggressive China.

The reason for Hawaii’s exclusion is a bit of geographic fine print in the treaty that founded NATO, signed 10 years before the archipelago became a state.

Article 5 of the treaty states that an attack on one NATO member is an attack on all, but Article 6 clarifies that such protections only apply to land, forces, vessels or aircraft north of the Tropic of Cancer. Hawaii, as well as the U.S. territories of Guam and Puerto Rico, are south of that line. American Samoa, the Northern Mariana Islands and the U.S. Virgin Islands are also south of the Tropic of Cancer.

Hawaii’s distance from the rest of the United States and its relative proximity to Asia create distinct security concerns. In 1941, a surprise attack by Imperial Japan on the U.S. naval base at Pearl Harbor in Honolulu caused the deaths of 2,393 Americans and led the United States to join World War II.

Hawaii is thought to be a likely target if North Korea were to strike the United States. An alert that was blasted to Hawaii residents erroneously in 2018, declaring a “BALLISTIC MISSILE THREAT INBOUND TO HAWAII,” caused widespread chaos throughout the state. “Is this the end of my life?” one resident later recalled thinking.

Security threats from and to Asia-Pacific nations were part of discussions at the gathering this week in Washington, which was attended by officials from the “Indo-Pacific 4” — Australia, New Zealand, South Korea and Japan.

NATO this week scolded China for becoming a “decisive enabler of Russia’s war against Ukraine,” adding in its “Washington Summit Declaration” communiqué that Beijing’s “stated ambitions and coercive policies continue to challenge our interests, security and values.” The alliance has recently tried to straddle addressing concerns in Asia while also not straying too far from its focus on Europe. Plans for a NATO liaison office in Tokyo appear to have fizzled.

A State Department spokesperson said the department received the letter and will “respond once we have an opportunity to review it.”

Schatz questioned Blinken about the matter at a Senate hearing in 2022, saying he didn’t have “any doubt that the entire free world would rally to our defense, but this is no small problem.” Hawaii is not covered while the other 49 states are, he told Blinken. “What are we going to do about that, Mr. Secretary?”

Blinken said he was confident that “any attack on the United States or its territories, even if outside the geographic scope of Article 5” would draw a response from allies.

He added that any effort to amend the treaty to include Hawaii would be “unlikely to gain consensus” because other allied nations also have territory outside the geographic scope of the agreement. (Martinique, an island in the Caribbean home to nearly 400,000 people, is a French “overseas department” south of the Tropic of Cancer.) Such a discussion would “open something of a Pandora’s box,” Blinken said. “I’m not sure that we could get there.”

Still, the senators argued that potential conflict in the Pacific could pose a threat to Hawaii and that “the scars of the attack on Pearl Harbor are still visible today.”

Justin Kranzl, a 53-year-old communications executive who recently moved to the Hawaiian island of Oahu, said he was unaware that Hawaii was technically outside of NATO’s geographical purview. Finding out that a state that has “been the subject of aggression” previously is excluded from NATO protection was “alarming,” he said.

David Serpa, a 35-year-old arborist who also lives on Oahu, said he hadn’t spent much time considering Hawaii’s exclusion from NATO protection, at least on paper, but added that it was “not surprising,” considering how separate Hawaii can feel from the mainland United States.

Should Hawaii come under attack, NATO allies would probably be drawn in anyway as the islands are “overrun” by the U.S. military presence there, Serpa said.

“We’re just so heavily militarized here that it’s almost redundant,” he said. “It just feels implied.”