The Minister for the Environment, Mr Martin Cullen, today gave the go-ahead for work to resume on the M50 motorway in south Dublin.
Work on the project had been halted following protest by campaigners seeking to preserve the medieval Carrickmines Castle site.
Announcing his decision, Minister Cullen said: "This decision is based on my overall assessment that the public interest in allowing construction of the South Eastern Motorway along its approved route justifies consenting to/approving of the works impacting on archaeology at the site."
He said: "It has been satisfactorily demonstrated that a systematic approach has been adopted by the Council to the archaeological resolution of the Carrickmines sites."
The Council's compromise plan will preserve parts of the site but others will be removed.
Campaigners claim this is not enough and that the whole site could be preserved if the road was slightly redirected.
Mr Cullen said as many as 130 archaeologists have been employed on the Carrickmines site and the archaeological mitigation to date is estimated to have cost €6 million.
The Minister said he considered 23 submissions relating to the case, 17 supporting early completion, with six objecting.