The D.C. Council set aside $6 million last spring to help D.C International — a new language immersion charter school for students in grades six through 12 — renovate its home-to-be, a building on the site of the old Walter Reed Army Medical Center in Northwest Washington.

But now it appears the school won’t get that money, at least not right away. Mayor Vincent C. Gray (D) is seeking to shift the $6 million to other projects, in part because ownership of the Walter Reed building hasn’t actually been transferred to the District yet.

Gray also said that the money — capital funds backed by long-term financing — can’t legally be used for charter schools, because charter schools are independent nonprofits and not part of the government.

That echoes a recent opinion from the city’s attorney general, Irvin B. Nathan, who wrote in a Feb. 19 letter that capital funds backed by income tax-secured bonds cannot be used for non-governmental entities.

“Charter schools are not part of the District government and, therefore, charter school capital projects are not District government capital projects,” Nathan wrote, outlining his interpretation of the legal differences between charter and traditional schools — differences that are sure to attract wider attention as fast-growing charter schools enroll a growing proportion of D.C. students.

Because they are organized as private nonprofits, charter schools function as public schools but they are not the same as public schools. Charters aren’t subject to the Freedom of Information Act, for example, nor to open-meetings laws that govern public bodies.

D.C. International is a joint effort of five language-immersion charter schools, who have banded together to form a secondary school where students can continue their language studies. Many parents, anxious about finding quality middle and high school options, have embraced the concept and are eager for the school to open.

Mary Shaffner, D.C. International’s chief operating officer, said the $6 million city grant is “critical” for the planning phase of the building project. Shaffner said the best-case scenario is that DCI could open its doors at Walter Reed in fall 2015, although it is not clear whether that is possible, especially given the loss of grant funds.

“We’re just investigating what it means right now,” Shaffner said.

D.C. Council member David A. Catania (I-At Large), who inserted the money for D.C. International into this year’s budget, said he doesn’t agree with Nathan’s legal reasoning and is determined to find a way to fund the project.

“Here you have five extraordinary, stellar public schools, that happen to be charter schools, coming together to create what is perhaps the most exciting education opportunity in terms of middle school and high school that anyone can remember,” Catania said. “And the government cannot find $6 million to fund this? I just think it’s laughable.”

Catania, who is contemplating a bid for mayor, said he would explore using paygo capital, which are not borrowed dollars and have far fewer strings attached.

The city has used paygo in the past to help fund charter schools’ $3,000-per-student facility allowance, money meant to go toward rent or mortgage payments. Pedro Ribeiro, a spokesman for Gray, said rules governing paygo dollars have tightened since then, and would no longer be available for charter schools.

“We do not use capital budget money, paygo or otherwise, to subsidize nongovernmental private uses,” Ribeiro said.

A spokesman for the Office of the Chief Financial Officer has not responded to questions about the rules for paygo capital.