The lawyer, whose identity has not been disclosed, was providing legal advice to the woman during a custody case in May 2007. The pair started an intimate relationship in circumstances they both dispute.

But their affections soured later that year.

The woman complained about the lawyer's conduct to the Law Society of the ACT in October 2007, prompting an investigation.

The lawyer had also earlier acted for the woman's sister as she sought to revoke a personal protection order in the Magistrates Court. She also complained about him to the Law Society, in November, prompting a second investigation.

Eventually, the Law Society took the lawyer to court for unsatisfactory professional conduct and professional misconduct.

The society's first complaint against the lawyer was that he had not been honest with it about the intimate relationship, instead telling it the sexual relationship had not started until after he acted for the woman.

It also alleged the lawyer failed to act honestly and in good faith when representing the woman's sister and improperly intervened with a potential witness.

He was eventually found guilty in the ACT Civil and Administrative Appeals Tribunal and was barred from further practising as a lawyer.

But he fought the decision, appealing in the ACT Supreme Court on 13 different grounds.

Justice Richard Refshauge, who delivered the court's judgment this week, dismissed the lawyer's challenge to the ACAT's decision.

He confirmed that the matter would go back to ACAT to give effect to its orders.

The lawyer was also ordered to pay the Law Society's costs.