The ARB was left 'surprised and shell-shocked' after a Professional Conduct Committee threw out a case that hinged on the Human Rights Act.
The case against Gavin Thomson was dismissed on the grounds that it breached the act, which says that a person facing a charge is entitled to a hearing within a reasonable period of time.
The ARB says it is the first time such an argument has scuppered a case.
Thomson, of Crieff, Scotland, was commissioned to work on an extension to a small house in Edinburgh, but relations with the client soured in 1994 and the latter started court proceedings.
ARB chief executive Robin Vaughan said Thomson's insurers settled out of court for £120,000 in 1999 and only then did the case come to his attention. But it was not until 2001 - seven years after the spat - that the client's solicitor reported the matter to the board. Thomson faced four charges, including failing to advise on the employment of contractors or the tender process, and abandoning the commission during construction. The ARB also claimed he withdrew money from the client's bank account without authority to make project payments, and that 'the design and detailing of the project was of poor quality resulting in the works being demolished'.
But the PCC, which acts independently of the ARB, dismissed the case. 'At this stage we were not concerned with the merits of the case but with article six of the human rights legislation, ' said its report. This says a person is entitled to a fair trial 'within a reasonable time', and those words had 'caused a great deal of thought', it added.
Vaughan told the AJ he was 'surprised and a little shell-shocked' by the decision. He said architects had rights of appeal but not the board. 'I have to accept the decision of the PCC, it's independent.' He added: 'There is a legal convention [that says] people like us don't make a move until civil litigation is finished. But if we are going to run out of time by waiting for the courts to finish, we will always be too late. I don't know what the courts would think if we started proceedings contemporaneously.'
Thomson was not available for comment.