The Glen of the Downs in Co Wicklow, scene of recent clashes between anti-roads protesters and Wicklow County Council, has been closed to the public by order of the Minister for Arts, Heritage, Gaeltacht and the Islands, Ms de Valera.
The closure relates to the entire glen, not just the areas which are being used as a camp site, or as a location for tree houses, and includes a number of nature trails and popular walking routes.
A spokesman for the Minister also said it was intended to place a public safety notice in today's newspapers to declare that the nature reserve was closed and that the move was "until further notice".
The move was made possible by the original High Court case between the anti-roads protesters and Wicklow County Council in which a ruling was made that, in effect, there were no rights of way in the glen.
The High Court found that people who enjoyed the amenity only did so with the permission of successive authorities which had responsibility for the glen.
The move is primarily aimed at the anti-roads protesters' camps and tree houses although, as the court also found, some of the land on which the tree houses and camps are located belongs to the county council, not the Minister. The council has already indicated its wish that all non-authorised people leave its lands which are earmarked for the road-widening scheme.
It is expected that the council will now go ahead with moves to have the protesters evicted, and the closure of the nature reserve will leave them with no legitimate reason to continue in the glen.
According to notices erected in the glen yesterday and which form the basis of today's newspaper advertisements, "structures, devices and tunnels have been erected and excavated at the Glen o' the Downs in Co Wicklow which make it unsafe for the public to visit, and which have caused damage to the nature reserve."
The notices continue that the Minister "regrets having to take this decision but deems it necessary in the interest of public safety and the protection of the nature reserve".
The anti-roads protesters themselves were not overly surprised by the action yesterday. One said: "Suggesting that this is being done to protect the nature reserve when the Minister knows it is being done to facilitate the arrival of chainsaws is a little ridiculous".
Last night, the Green Party called on the Minister to resign over her handling of the glen issue.
A statement said the Minister had shown disregard for the nature reserve for which she was responsible.