Dean of law at the University of Canterbury Ursula Cheer said the section of the Summary Offences Act 1981 which the defendant was charged under refers to people using "obscene or indecent" language within hearing of a public place.
She said the section was "meant to deal with issues around public order".
Associate professor of law at the University of Auckland Kenneth Palmer said writer and broadcaster Germaine Greer was charged with swearing in public in 1972 in New Zealand, he said.
The charges follows another case currently going through the court process where a woman in her 20s allegedly told a man "Go back to your country" with intent to insult him. She also faces charges of assaulting the man, wilful damage, and possessing meth.