A landmark case testing the effectiveness of Australia's anti slavery laws will go before the High Court today.

The case involves the owner of a Melbourne brothel, who in 2006, was convicted of possessing sex slaves, namely Thai women smuggled into Australia.

Wei Tang successfully appealed against her 10 year jail term and conviction.

The Commonwealth Director of Public Prosecutions is now appealing against that ruling and the matter has been set down in the High Court for two days.

Wei Tang's lawyers are expected to argue that the legislation is unconstitutional.

An organisation which works with trafficked women says the outcome of the case could have implications on Australia's anti slavery laws.

Nina Vallins from Project Respect, says the case is the most crucial test of the effectiveness of the laws on slavery ever to go before an Australian court.

She says the victims in this case have been in virtual limbo for five years.

Ms Vallins says more support should be offered to the victims of sexual slavery.

"The Australian Government only offers visas to women who are persons of interest to the police," she said.

"So that if the police are interested in investigating their case and the women are able and willing to co-operate, then the women can access a comprehensive system of support."

"If police aren't interested in investigating the case then the women are returned home," she said.