A federal judge will let groups suing the Obama Foundation over its plans for a presidential center on Chicago’s South Side begin demanding information from the city of Chicago to determine how the site was selected for the project instead of other private properties.

In a hearing late Tuesday, District Court Judge John Robert Blakey agreed to let the plaintiffs, led by Protect Our Parks, obtain information from the city of Chicago and Obama officials on how it selected the site. The Barack Obama Presidential Center is being proposed on federal land that was deemed by the government in 2012 to be inappropriate for construction.

“The court hearing brought together a bunch of our supporters and it brought us closer,” Protect Our Parks President Herbert Caplan, told the Chicago Tribune. “It further motivates us to press on. We will keep doing what we’re doing.”

The Tribune said lawyers for groups opposing the project will be able to subpoena officials to learn more about the project.

Protect Our Parks, along with Charlotte Adelman, Maria Valencia, and Jeremiah Jurevis, in May sued to "bar the Park District and the city from approving the building of the presidential center and from conveying any interest in or control of the Jackson Park site to the [Obama] Foundation."

The organization stated that the University of Chicago's bid to house the building on historic park land that is protected by preservation laws would be a violation of federal and local policy. Protect Our Parks said public park land is "prohibited by law" from being handed over to a nongovernmental entity for private use, and that it would violate the park district code.

The Obama Foundation had originally proposed in 2015 having National Archives oversee the project when it was supposed to be just a library. But the project has evolved into the current $500 million development that wants to build a privately run, 23-story facility on protected land.

[Also read: Obama Presidential Center's groundbreaking date pushed back]

The lawsuit said it's an "institutional bait and switch," according to a copy of the complaint obtained by the Washington Examiner.

The Chicago City Council voted in June to allow 19.3 acres of Chicago Park District land in Jackson Park to be leased by the city of Chicago to the Obama Foundation. The park is near the Museum of Science and Industry, Lake Michigan and the eastern edge of the university campus, where Obama used to teach constitutional law.

The Obama Foundation has not disclosed how much it will have to pay for the land or why it selected the historic land instead of privately owned lots for sale. But two conservation experts with knowledge of the legal land transfer process told the Washington Examiner the city will charge Obama close to nothing for the land.

The lawsuit also stated the Park District does not have the right "to transfer valuable public trust land for virtually no compensatory return.”

While the legal case continues, the foundation is waiting on federal review by the Environmental Protection Agency, a requirement outlined under the National Environmental Policy Act and Section 106 of the National Historic Preservation Act.

The first verification process will determine if the Obama Presidential Center would have "adverse effects" on Jackson Park. The State Historic Preservation Office will ask "official consulting parties" to provide opinions on whether it would have adverse effects on the land.

"This isn’t just any public open space; this is historic parkland originally designed by Frederick Law Olmsted, Sr., and Calvert Vaux (of New York’s Central Park fame),” one of the consulting parties, the Cultural Landscape Foundation, states on its website. The park system was designed in 1871, and Olmsted wrote in 1895 that the Museum of Science and Industry was intended to be the only "dominating object of interest" in the park.

In 2012, Jackson Park was at the center of another Section 106 compliance review, and officials decided it should not be touched.

The judge also said he will not stop the foundation from relocating a track field from where the Obama center is asking to be built to a different location, as preparation for the still-unapproved project.

As far back as January, orange dots on trees in Jackson Park were reported. The dots indicated those trees would be chopped down to make way for the existing track and field site, which was being relocated so the Center would be built on the current property.

As of early August, 40 of those 300 trees were reported by the Architect's Newspaper as having been chopped down to make room for the new track field.

But eight months ago, Obama Foundation CEO David Simas promised that until they obtained permission from the Interior Department that they were could proceed with the plan, "there will be no trees removed or cut down."

Photos of the Jackson Park baseball field showed it had been dug up in order to house the track field.

The foundation said last week its promise not to cut down trees was in regard to the 19.3 acres where the center will be built, not on the other park land where the track field is being moved.

The Cultural Landscape Foundation said the bigger issue is that the trees are only being cut down because they are part of a project connected to the center, despite saying otherwise earlier.

"If the Obama Foundation can’t be trusted on what 'no tree removed or cut down' means, how can they be trusted on their other assurances?” Charles Birnbaum, president and founder of D.C.-based nonprofit group the Cultural Landscape Foundation, said in a statement.