Republican Sinn Féin claims gardaí used "bullyboy tactics" during an annual commemoration for Fergal O'Hanlon in Monaghan Town on Sunday.
Fergal O'Hanlon was killed on New Years' Day in 1957 while taking part in an attack on an RUC barracks in Brookeborough, Co Fermanagh.
Republican Sinn Féin claim gardaí "stormed in on marchers" at Latlurcan and "dragged a young man across the road", something the group says "terrified" young children who were present.
The group further claims that the man in question gave his name to gardaí in Irish and was then "accused of giving a false name".
In a statement to Northern Sound, gardaí confirmed that a man in his late 30s was arrested at Latlorcan on Sunday.
Gardaí say the man was taken to Monaghan Garda Station, where he was released without charge, and a file will now be forwarded to the DPP.