The rule requires athletes to notify testers of their whereabouts three months in advance and must specify one hour each day as to where and when they can be tested.

The challenge relies on the Belgian constitution and the European Convention on Human Rights and Fundamental Freedoms of the Council of Europe to claim the rule is an invasion of privacy.

The group, comprising footballers, cyclists and volleyball players, filed the case with Belgium's Council of State court, which may take up to six months to issue a ruling.

Paul Horvath, a solicitor at boutique firm Sports Law who previously defended Australian swimmer Ian Thorpe against allegations using of performance-enhancing drugs, told Lawyers Weekly that the case could have implications for Australia.

"If they were to decide based on the European Charter there has been a breach of individual rights, I would think that is something that other countries would have to recognise...," he said.

Horvath has routinely used the European Charter of Human Rights in cases in front of the Sydney-based Court of Arbitration for Sport which could "possibly be heavily influenced by any such decision" made in Belgium.

Michael Conn, partner at Teakle Ormsby Conn, told Lawyers Weekly that WADA is constantly changing the rules and has recently introduced two new directives for rugby league players.

One rule is that WADA is to be notified if a player is put on an intravenous drip and the other involves testing athletes pre-season to determine if they are asthmatics.

"Now there are people who if you tested them today, would not test as being asthmatic. Yet out on the field under the stress and the exercise they can end up with breathing problems," Conn said.

"So what does that mean? Does that mean you don't give them Ventolin? So some of these rules can be pretty onerous and in many ways, in my opinion, quite stupid."

The Belgium athletes stressed they were not opposed to out-of-competition testing but claimed the current system was far too invasive, forcing them to pinpoint even if they were going to the movies.

WADA has maintained the changes make it easier for athletes to abide by the whereabouts rule, including limiting mandatory location specification to one hour a day.

- Sarah Sharples