A man was arrested after he refused to wear a face covering on a bus or give his name to gardai who were called to the scene.
The agitated individual, who was subsequently charged with a public order offence, became embroiled in a heated verbal row with the driver.
Gardai were alerted by the Bus Eireann employee after tensions quickly escalated on the vehicle at Main Street, Ballyhaunis, Co Mayo on Tuesday.
The man, in his 40s, is due to appear in Castlebar District Court next Tuesday.
A Garda spokesman said: "Gardaí attended a public order incident in the Main Street area of Ballyhaunis that occurred on Tuesday at approximately 4pm.
"A man aged in his 40s has been arrested and charged in relation to the incident.
"He is due to appear before Castlebar District Court next [Tuesday]."
It is understood the charge, while not directly related to the new face masks laws, is the first public order offence connected to a refusal to wear a face covering.
The new legislation came into effect on Monday and it made the wearing of face-coverings on public transport compulsory to help curb the spread of Covid-19.
Dermot O'Leary, the General Secretary of the National Bus and Rail Union, insisted a special Garda public transport unit should be set-up.
He stressed that bus drivers have enough to worry about without being left in a position where they have to watch who is wearing face-masks and police the law.
He said: "There has been many times that a bus driver has to call the Gardai for what is technically a public order offence.
"This is similar to that but it's new in the context of face-coverings.
"At a point in time fare evasion was very high, but it's down to a minimum now.
"And there's a reason for that and that is the transport companies have dedicated units that were spot checking people.
"And that worked over a period of time.
"It may be something like that [which is needed], where an agreement for a certain unit that are trained in the procedures of the law could come in and work the oracle so to speak."
People who do not wear a face covering risk a fine of up to €2,500 and the prospect of a six-month jail sentence.
Drivers can request people wear a face mask and are entitled to refuse members of the public entry or order them to leave the bus.
Gardaí can also be called to deal with any related issues under the legislation.
Mr O'Leary continued: "A lot of people are complying in very high numbers, but of course there's a difference between policing something and encouraging people.
"Bus drivers, by and large, and railway station staff, they have a relationship with regular travellers and they can have conversations.
"But, in terms of enforcement and policing the bus driver has a hard enough job and indeed the railway worker has a tough enough job without policing it.
"So, if they're not doing it and the Gardai are certainly not doing it, quite rightly from their point of view, then something needs to give."
It is understood the man claimed he had a disability, which meant he could not wear a face covering.
