Three people have been removed from trains for refusing to wear face masks, since their use became mandatory on Monday.
Anyone who is found to break the law can be fined or face a prison term.
It comes as the government works on regulations to enforce the use of face coverings in shops and supermarkets.
Irish Rail's Barry Kenny says: "If we need assistance for anything in relation to anti-social behaviour, if our staff feel the need to get support from gardai, we don't want to be rowing with customers."
