The action is being taken by Gordon Lucas, who is seeking to enforce EU directives on national monuments. He is seeking an injunction and a declaration that the National Monuments Act 2004 is in breach of EU law.
Lismullin was declared one of the top 10 most important archaeological discoveries in 2007 by Archaeology magazine, published by the Archaeological Institute of America. The Hill of Tara has also been placed on the 2008 list of 100 most endangered sites by the World Monuments Fund.
Last year, archaeologists working on the route of the motorway stumbled on a vast Iron Age ceremonial enclosure, or henge, surrounded by two walls.
The 2,000-year-old site is about 2km from the Hill of Tara. The discovery of the henge, measuring about 260ft in diameter, confirmed the long-held belief that the area contains a rich complex of monuments.
The extent of archaeological remains on the Hill of Tara — burial mounds, religious enclosures, stone structures, and rock art dating from the third millennium BC to the 12th century AD — makes it Ireland’s most spiritually and archaeologically significant site.
Lismullin and other sites that stand in the way of the new motorway are now approved for destruction. Although archaeologists are rallying support worldwide for the protection of the Hill of Tara, the iconic site remains in great peril, according to the lobbying group Tara Watch.
The European Commission has initiated legal action against the Government over the M3, charging Ireland with failing to protect its own heritage.
A Red C opinion poll has found that almost two-thirds (62%) of Irish adults agree that the current format set down for the M3 is wrong, and that alternatives should be found to protect the heritage sites.
More than half (58%) support a proposed heritage park solution, while 31% agree they would prefer to keep the M3 running through the valley as already agreed.
Vincent Salafia of protest group TaraWatch said: “This is a parallel case to the case being taken against Ireland by the European Commission, which states the Irish government is in breach of EU law. Work should cease immediately within the Tara archaeological complex, until this matter is resolved.
“It is ironic that the Irish government is pushing its citizens to adopt the Lisbon Treaty, while they flatly refuse to obey current EU law with regards to protection of the environment and the national monument at Lismullin,” said Mr Salafia.