But a bid by the former marathon champion to have William John Bell treated as a vexatious litigant is unresolved.

It is the fourth time the ACT Civil and Administrative Tribunal (ACAT) has knocked back Mr Bell's long-running claim that Mr de Castella had employed him as a coach to marathon runners in the Indigenous Marathon Project.

The program trained indigenous athletes, from April 2009 to November 2010, to run in the New York marathon.

Mr Bell was not paid for his work but was reimbursed for expenses and provided with a laptop computer and mobile phone.

He was dropped from the program in 2010 after a dispute with Mr de Castella.

Mr Bell then launched a series of actions in the ACAT against Mr de Castella and Smart Start for Kids, in which he claimed he was owed $10,000 in wages.

But the tribunal found Mr Bell had worked as a volunteer.

Mr Bell appealed the decision, arguing the tribunal had erred in refusing to allow him to use certain information at hearing.

The information included witness statements and documents from the Health Department that he claimed demonstrated there had been an employment agreement between himself and Smart Start for Kids.

Mr Bell argued the unsatisfactory nature of the original proceeding meant the tribunal should make a fresh determination about his employment status.

He said a failure to do so would be an injustice.

But Mr de Castella argued the tribunal was not legally allowed to rehear the matter.

The ACAT was asked to treat Mr Bell as a vexatious litigant in future, which would prevent him bringing proceedings against Mr de Castella or Smart Start for Kids.

ACAT acting presidential member Chris Chenoweth, in a judgment published on Thursday, said Mr Bell could not re-litigate the case.

"The tribunal is bound by the principle of res judicata to not allow that issue to be re-litigated in these proceedings," he wrote.

"The law on the matter is clear, and the law [and the policy behind it of not exposing a respondent to repeated claims on the same ground that has been found against the applicant in the past] must be upheld.

"The decision of the appeal tribunal on the claim for remuneration as an employee is to confirm the decision … and as a result to dismiss this appeal."

But Mr Chenoweth ordered Mr de Castella to make a separate application to have Mr Bell declared a vexatious litigant.

An application for costs by Mr de Castella was also dismissed.