A man accused of turning his garage into a den for child abuse will stand trial again after earlier being acquitted of sex crimes.

In a decision released today, the Court of Appeal ruled the man must face a retrial for allegedly forcing his 11-year-old son and two friends to masturbate in front of him.

The alleged offending took place in the man's garage, where he stored computers, remote control models and pornography.

He allegedly asked the boys to masturbate to a pornographic movie on a number of occasions in 2011, including offering to instruct one of the boys how to do it.

The boy turned the offer down and another boy described the request as "creepy", but the boys, aged 11 and 12, eventually complied, the Court of Appeal said.

At the man's trial in the Auckland District Court in January, his defence lawyers successfully argued the accused had not committed a crime.

The Court of Appeal said District Court Judge Edwin Paul had "reluctantly" dismissed the case after ruling the man did not carry out sexual acts "with" the boys.

Defence lawyer Chris Wilkinson-Smith argued at the trial that at no time did the defendant touch the alleged victims or indulge in sexual activity himself.

However, in today's ruling, Justice John Priestley found the man should stand trial again.

Justice Priestley said the act could be deemed criminal because the man had actively encouraged the boys to masturbate.

It is rare for an acquittal to be overturned.

All names are suppressed in the case to avoid identifying the victims.