The High Court has declared that the area of Moore Street in Dublin that should be declared a national monument is wider than that designated by the Minister for Arts and Heritage.
Mr Justice Max Barrett gave his ruling in a case taken by Colm Moore as a nominee of the 1916 Relatives Association.
He has restrained the minister from carrying out any further works to numbers 13-19 Moore Street until she has had an opportunity to consider the judgment and how she intends to proceed.
Mr Moore took the action after numbers 14 to 17 on Moore Street were designated national monuments by the minister.
The buildings are believed to be the last buildings where the leaders of the 1916 Rising gathered prior to their surrender and execution.
Mr Moore and the association claimed the designation should have included lands and buildings of the terrace at numbers 13, 18 and 19 as well as a number of basements and cellars.
Members of the association said it was a great day for the people of Ireland.
Jubilant 1916 Relatives Association outside High court. pic.twitter.com/ung2pCr1ZB— Orla O'Donnell (@Orlaodo) March 18, 2016
The judge said the Easter Rising was unique and the GPO occupied an iconic position in Irish history.
He said the Moore Street battle site was uniquely worthy of commemoration.
The judge also ruled a banner erected on numbers 14-17 must be taken down as it constitutes unauthorised development.
Minister Heather Humphreys and her officials said they will carefully study today's High Court judgment.
The minister said: "This was a complex case and the judgment, which runs to more than 400 pages, needs to be studied in detail.
"My priority up to this point has been to progress the important works to preserve the National Monument at No's 14-17, which was the final headquarters of the 1916 leaders.
"My officials and I will consider this judgment in detail before making any decisions on further actions."
The minister said she regrets that the public will not now be in a position to access 14-17 Moore St during the centenary period as had been planned.
Relatives Association celebrates 'amazing day'
Speaking outside, James Connolly Heron, great grandson of James Connolly, and a member of the association, said the decision was the culmination of a decade-long campaign where the citizens of Dublin came together to protect and preserve the very birthplace of the Republic.
He said they stood together in principle for over a decade, against great odds, almost the same as the odds the volunteers of 1916 went out to meet.
Mr Connolly Heron said this was an amazing day. The High Court backed them, as well as every political party in the country, he said.
There was not anyone who supported the idea of building a shopping centre on the Moore Street battlefield site, he added.
Mr Connolly Heron said you would hardly build a shopping centre on top of this sacred ground.
He said it was very fitting that on the eve of the centenary celebrations of this momentous, seminal moment in our history that the last extant battlefield would not be subjected to the wrecking ball.