Whistleblower and former garda John Wilson was one of three men arrested at a water charges protest in Cavan on Tuesday.
Gardaí arrested the three at Kilnavara Crescent in Cavan town at about 9.30am.
The men are aged 21, 46 and 52 and they are being held at Cavan Garda station.
A Garda spokesman could not confirm the identities of those arrested, but it is understood one of them is Mr Wilson.
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Mr Wilson came to prominence after he reported the widespread and inappropriate cancellation of penalty points.