After a 25-year absence, the United States is poised to operate in the Philippines once again — but it will first need clearance from the Supreme Court in Manila.

Since 1898, the Subic Bay Naval Base provided the US military with an important staging ground for security operations in the Western Pacific. President Corazon Aquino ordered the US military to depart in 1992, however, following failed negotiations to extend base leases over multiple issues, including the presence of nuclear weapons, which is still a sticking point with the Philippine government.

Times — and the security dynamic in Asia, particularly in the South China Sea — have changed.

Currently, US forces can reach the South China Sea from bases in Japan or Guam, but a presence, even rotational, at Subic Bay would allow for a faster response to contingencies.

Subic Bay is strategically located on the western side of the main Philippine island of Luzon, facing the South China Sea. The enormous base — roughly three and half times the size of Washington, DC — sits only 145 nautical miles from Scarborough Shoal, the site of an ongoing squabble between the Philippines and China that reached new heights of tension during a three-month standoff in 2012, after the Philippine Navy discovered Chinese fishing vessels there carrying illegally-collected coral and marine life on board.

Two years and eight rounds of discussions later, in April 2014 the US and the Philippines signed a 10-year Enhanced Defense Cooperation Agreement (EDCA), providing the US with greater access to Philippine military installations. The EDCA is part of President Barack Obama's "pivot to Asia," which has also included visible military force upgrades in Australia and Singapore.

Several factors paved the way for the return of US forces to the Philippines. One was a positive view of the US military among Philippine citizens following its quick response in 2013 to Typhoon Haiyan; their own government's response to response to the deadliest typhoon recorded in modern Philippine history was notably slow and disorganized. China's effort to expand its authority in the South China Sea was another factor.

But before heading back to Subic Bay, the Philippine government needs to settle a few legal questions. Lawmakers will determine whether the new accord must be ratified by the Philippine Senate as a treaty or if the new accord is merely an extension of older agreements and thus does not need ratification. Because the 1987 Philippine constitution prohibited foreign bases on Philippine soil (although existing bases were grandfathered in), the country's Supreme Court has also been considering the constitutionality of the pact.

"Given the ongoing Philippine Supreme Court review of the EDCA's constitutionality, the DoD and DND [Philippines Department of National Defense] have agreed to delay implementation of the agreement," said Commander William Urban, a Pentagon spokesperson. "There have been informal, working-level discussions of potential locations and next steps, but no final decisions have been made nor are there any plans to begin implementing the EDCA until the Supreme Court completes its review."

Proponents of the deal point out that the EDCA will permit only rotational deployments, and that the US will hold no bases on Philippine soil.

Jose Cuisia Jr., the Philippine ambassador to the US, told VICE News that his country is enthusiastic about welcoming US forces back on its soil. He added that an agreement might be reached concerning two or three locations, but noted that all parties were still deliberating and would not move forward until questions of constitutionality and ratification were settled. The key, Cuisia emphasized, was that "there will be no bases; US forces would come on a rotational basis only, in accordance with our constitution."

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A US territory beginning in 1898, the Philippines were taken over from Spain following the Spanish-American War and finally gained independence in 1946. The country signed a Mutual Defense Treaty with the US in 1951, and the Philippines remains one of five such US treaty allies in the Asia-Pacific (along with Australia, Japan, South Korea, and Thailand). The US maintained several major military bases as part of the defense treaty, notably Subic Bay Naval Base and Clark Air Base, which continued to see heavy use in the decades following the 1951 treaty's ratification.

In 1991, nearby Mount Pinatubo erupted, burying both Subic and Clark in volcanic ash. Clark was declared a total loss and Subic, though salvageable, lay beneath a foot of ash. Later that year, negotiations to extend the US military presence in the Philippines broke down and the Philippine Senate terminated the US basing agreement. President Aquino ordered the US military to depart by the end of 1992.

Following the American departure, the government renamed the area the Subic Bay Freeport. Now a special economic zone that is roughly the size of Singapore, it has become a popular tourist destination bolstered by low taxes and duty-free import privileges.

Beginning in 2000 after the completion of a Visiting Forces Agreement (VFA), US ships started making visits to the Philippines again in support of military exercises and for resupply and repair. The annual Balikatan ("shoulder-to-shoulder") bilateral military exercise also resulted from the VFA.

Negotiations for the current EDCA took place over two years and eight rounds of discussion, according to the Philippine Ministry of Foreign Affairs. The presence of nuclear weapons remains a red line for the Philippines. The country is a signatory to the 1995 Southeast Asia Nuclear-Weapon-Free-Zone Treaty, and the EDCA states that US military material "shall not include nuclear weapons."

While the agreement has stalled somewhat, the Philippine government is moving forward with preparations for an enhanced US military presence. In April, Philippine General Gregorio Catapang told the Sydney Morning Herald that eight possible locations had been identified for US troop rotations, training, and exercises. Four are on the main island of Luzon, two are on central Cebu, and two are on the western island of Palawan.

In May, according to Philippine Defense Undersecretary Pio Lorenzo Batino, the country's military signed a 15-year renewable lease with the Subic Bay Metropolitan Authority, allowing the military to use certain areas of the Subic Bay installation. The Philippine military has never used the Subic Bay Naval Base, but now looks to station its fighters and frigates there and take advantage of its proximity to the South China Sea.

Final rulings on the questions of constitutionality and the role of the Philippine Senate could come by the end of the year, delaying implementation until the are resolved. "If we formalize (now) and they start putting up structures and it's not constitutional, they will have to destroy those structures," Catapang said.

Manila will host the annual Asian-Pacific Economic Cooperation meeting in November this year, which Obama plans to attend. The US has provided $300 million in military assistance to the Philippines since 2001 and plans to provide an additional $40 million in 2015.