A WA judge has ruled against a man who argued he could not wear a bike helmet because he was wearing a kippah - or Jewish skullcap.

Justice David Allanson handed down the decision this week after Simon Thomas sought to have his conviction overturned.

Mr Thomas was originally convicted for failing to wear a bike helmet while "scooting" down Barrack St in February last year.

During his trial in Perth Magistrate's Court, he argued he couldn't wear his bike helmet because he was wearing his kippah.

He also argued that he wasn't actually riding his bike but was "next to it" and that he was "scooting" or "coasting" because he had his left foot on the right pedal.

However the magistrate disagreed and he was convicted of not wearing a helmet.

Incensed by the decision Mr Thomas took the matter all the way to the WA Supreme Court arguing the magistrate refused to allow him to refresh his memory during the initial trial, and that his finding was based on "inadmissable testimony".

He claimed an experiment to test the "scooting" theory conducted by one of the police officers who issued the fine should not be relied upon.

During the original trial, Mr Thomas told the court a few weeks after he received the traffic infringement he realised it was the day of his birthday, which he said was one of three days a year he wore his kippah.

He said he could not wear his helmet while he was wearing a kippah. However, he also said he would "not generally" or "not necessarily" wear it.

The magistrate found there was a reasonable possibility that Mr Thomas was wearing a skullcap, highlighting that there was exemptions in the legislation for religious and cultural reasons for not placing anything over the skullcap.

But he ruled that there was no evidence the skullcap made wearing the helmet impractical.

In handing down his decision whether to grant leave to appeal, Justice Allanson said this week that he was satisfied the magistrate's decision was correct and that there was no "substantial miscarriage of justice".

"There was no evidence to raise the issue of whether the wearing of a skullcap made wearing a helmet impractical," he said.

WA lawyer John Hammond said he supported the decision saying making exceptions for religious and cultural reasons would be "wrong".

"The Judge held that there was no evidence that wearing the skull cap made wearing a helmet impractical," he said.

"On a practical level I would say that a skull cap does not interfere with wearing a helmet.

"It would be completely wrong if wearing a burqa, a turban, biretta (Catholic religious cap) or skullcap could be used as a reason not to wear a helmet.

"The law should apply equally to all people regardless of religion colour or race.

"There is also a question of safety. There are good safety reasons why helmets are required."