Campaigners have failed in an attempt to challenge a decision by Gloucestershire County Council to close an environmental education centre.
Protesters had sought a judicial review after plans were announced to sell off the Wilderness Centre in Mitcheldean.
A judge at the High Court in London has ruled they do not have a legal argument to stop the closure.
The council said the site would now be sold on the open market as it needs to save money.
Trevor Roach, from The Friends of the Wilderness Centre, said he was "disappointed" with the decision.
"I'm hoping... we can now look at a viable future for it by keeping it as an environmental centre," he said.
"Environmental centres in the Forest of Dean provide a huge diversity of unique facilities.
"As a charitable trust we can have a development plan to develop an iconic environmental centre with enhanced services to the community.
"The council has every right [to sell it to the highest bidder] but I'm hoping they will look realistically at our proposal, because they are shooting themselves and the community in the foot if we miss this opportunity to do something better than raise a little bit of money quickly."
Will Windsor Clive, cabinet member for communities at Gloucestershire County Council, said: "This legal action has been a waste of taxpayers' money and a waste of time for Friends of the Wilderness Centre.
"We have acted entirely correctly throughout and we are grateful for the judge's endorsement of that.
"As we have said all along, we remain happy to meet with Friends of the Wilderness Centre to discuss their proposals.
"That meeting would have taken place several months ago, were it not for this legal action."
The plan to sell off the site is part of a move by the Conservative-run council to save £45m through the sale of buildings and land.