People are required by law to wear a face-covering on public transport from today.
Those who do not face a fine of up to €2,500 and the prospect of a six-month jail sentence.
Drivers can request people wear a face covering and can refuse people entry or order them to leave and gardaí could also be called to deal with any issues.
Dermot O'Leary, General Secretary of the National Bus and Rail Union, says members cannot be expected to enforce the rules alone.
"There is confusion now in relation to who's going to be policing this," Mr O'Leary said.
"The frontline transport staff that we represent will not be policing this. In other words, we're still confused in relation to who actually will be policing this new law. My understanding is the gardaí have no direct role in this.
We're a bit confused, and again the reason for our confusion is because we haven't been at the table where the decisions were made.
The general secretary of the Association of Garda Sergeants and Inspectors (AGSI), Antoinette Cunningham has said that enforcement powers for new regulations on the wearing of face coverings on public transport rest with transport operators and the National Transport Authority (NTA).
Regulations to enforce the compulsory wearing of face coverings on public transport come into effect today with fines of up to €2,500, as well as a possible jail sentence of six months for those who refuse to wear face coverings on public transport.
Under the new regulations a driver or other relevant person can request someone to wear a face covering. They can ask them to leave a vehicle if they are not wearing one, or refuse them entry. If a person does not comply, and does not have a reasonable excuse, gardaí could be called.
Ms Cunningham told RTÉ radio’s Morning Ireland that the statutory instrument for the regulations says that the responsibility for enforcement rests with the transport operator. While she acknowledged it was not a driver’s job to police the law, neither was it the job of the gardaí to check people on public transport, she said.
The regulations were clear, she said, when a driver asked a person to wear the mask and they refused, then the gardaí will assist.
The relevant person has to act in the first instance. When all those fail, we will then assist if required.
Ms Cunningham said this was another example of the lack of consultation between legislators and those who would be required to enforce regulations. There should be a better consultative process, she added.
When gardaí are called they will act, but the enforcement powers rest with “the relevant person” she said, which in this instance were the National Transport Authority and operators.
Ms Cunningham also queried if it was appropriate work for gardaí to go into pubs to check if food was being served, if social distancing measures were being observed and appropriate PPE was being worn by staff. The Health Safety Authority should surely be involved, she suggested.