Following a recent decision by the OPW, UAV are no longer permitted to fly at “National Monuments” in the Republic of Ireland without prior agreement. The decision was (rightly) taken for safety and nuisance reasons following several incidents.
A National Monument is a particular class of archaeological site ‘the preservation of which is a matter of national importance by reason of the historical, architectural, traditional, artistic or archaeological interest attaching thereto’. There are several hundred across the country; if you are unsure where these monuments are, there are lists arranged by county available here compiled by the National Monuments Service. There is also a Wikipedia page dedicated to the subject with links to Google Earth. This is not a blanket ban, it relates to a specific set of monuments in state care. Access may be granted, but permission is required.
The decision does not apply to the vast majority of archaeological sites on private land around the country (map here) where drone flying is (for the time being at least) still possible. These sites are on private land, so landowner permission is absolutely necessary. Do bear in mind that all archaeological sites have legal protection, and wilful or negligent damage is punishable by law.
However, responsible drone flight should not pose a threat to of our archaeological heritage if proper regard is given to safety precautions before take-off. There is probably little direct risk to earthen monuments from drones; however upstanding masonry structures (e.g. castles, abbeys, round towers etc.) should be given a wide berth (>= 30 m) in line with similar provisions for any upstanding structures or building (SI 563/2015). Take-off/landing in the vicinity of sites should be strictly avoided, as should flying within building interiors.
Safety is in everyone’s best interests; archaeological sites are often in a precarious state and should always be approached with care and respect. Further crash incidents will likely see an extension of the prohibition to all archaeological sites and monuments. This would be an unfortunate development; low altitude aerial photography has played a hugely important role in Irish archaeological research over the years and UAV have huge potential in archaeological mapping, prospection and conservation.