A judge has dismissed a charge of offensive behaviour against a woman who bared her breasts at a Destiny Church rally in downtown Auckland, saying "a bare-breasted woman can hardly be said to be an alarming sight".

Emma Jean Wills was protesting in March against the church's anti-abortion stance.

Wills, 20, of Wellington, was arrested in Queen Street two or three hours after the protest ended, still exposing her naked upper body.

She told Judge Caroline Henwood in the Auckland District Court she did not think it was illegal to be topless.

Her lawyer, Anthony Trenwith, argued that Wills' behaviour was not offensive.

She was part of a protest she felt strongly about. Wills thought she was entitled to be topless, and was not breaking the law.

In her written judgment delivered yesterday, Judge Henwood said: "The court finds that the defendant was topless as part of the protest ... and it may well be said as part of her protest her behaviour in that context was not offensive.

"After all, a bare-breasted woman can hardly be said to be an alarming sight and her intent as part of the protest was not to be lewd or offensive but to express her strong views relating to her opposition to the Destiny Church and their policies surrounding abortion and other issues."

The judge said that there had to be a balance between freedom of expression and the freedom of others to enjoy public places.

She said the police were right not to arrest Wills during the demonstration.

However, she was still topless some hours later, and the judge ruled that her behaviour at that time could be considered offensive. "The protest was over and she wanted to continue to be an exhibitionist in her own right and was now downtown in Queen Street amongst families who were going about their business and were no part of any protest."

The judge said she had no doubt that at that time, in those circumstances, Wills' conduct would be regarded as offensive by a "resilient, reasonable person".

The judge then noted that Wills was charged with offensive behaviour in Hobson Street, while the complaint against her related to her conduct in Queen Street, after the protest. The charge of behaving offensively in Hobson Street had not been proved beyond reasonable doubt.

Outside the court Mr Trenwith said the judgment upheld people's democratic right to protest and recognised that protest action could take many forms, including the unorthodox.