Chicago is protective of both its lakefront and its parks.

And that long-standing resistance to land grabs by the powerful, that communal loyalty to the dictate of “forever open, free and clear,” is why spending summer weekends walking or biking all along our waterfront remains such a pleasure.

Wise civic heads know that once high-value green space disappears, it tends not to return.

For that reason, even worthy projects slated for this precious public real estate are scrutinized from all sides in this town. Even projects such as the Obama Presidential Center.

Last week Judge John Robert Blakey of the Illinois Northern District Court ruled against a second attempt by the Protect Our Parks group (and some local residents) to stop construction on the Obama homage in Jackson Park.

This was a blow to those who have argued against building the center in its present location. And, reported the Chicago Tribune, it meant that the proposed groundbreaking on Aug. 16 can almost certainly proceed.

In essence, one camp argues the benefits to Chicago’s South Side will be most profound in this location and that green space will be respected. The other argues there could have been a smarter choice that still would have paid tribute to the history of the Obamas and what they mean to the South Side.

But the old saw has it that possession is nine-tenths of the law. Along those same lines, it is a lot harder to persuade a court to stop a project when the building is already rising from the earth.

What does Chicago expect from this project? How can it best partner for the benefit of its citizens, especially those living close? Those should be the discussions now in collaboration with the staffers and donors, prior to the projected opening in 2025. A lot remains undecided.

A presidential museum does not arrive every day nor even each generation. The deal is a trade-off, like most things in Chicago and most things in life.

Time now for everyone to move forward together. And for the Obamas and their supporters to live up to their ask.