Istanbul authorities had planned to rebuild an Ottoman-era barracks on the site of Gezi Park, one of the few green spaces in the city centre, at the fringes of Taksim Square.
But the construction was blocked by court order after the mass protests in May-June 2013 that snowballed into a wave of public anger against the rule of President Recep Tayyip Erdogan, then premier, and left eight people dead.
It denounced the authorities for putting "the pursuit of short term economic interests before our political, natural, historic and cultural assets" and said the decision was "evidence of the political pressure on the judiciary".
"The decision is devoid of all professional, ethical and scientific principles," it said.
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The group warned that "Taksim Square and Gezi Park are no longer just under the protection of Istanbul and Turkey but under the whole world".
However the ruling was never communicated publicly and was first reported by the Cumhuriyet daily on Wednesday, before being confirmed by Taksim Solidarity.
Turkish opposition newspapers said that the ruling had been made possible because of the support of three pro-government judges who had joined the body in 2014.