A three-year police inquiry found there were significant flaws in the building's design. But although police considered bringing manslaughter charges against both Reay and Harding, they decided not to prosecute as they would be unlikely to obtain a conviction.
Engineering New Zealand, the industry governing body, began an investigation into Reay but dropped it when he quit the body in 2014.
However, in December the High Court ruled Engineering New Zealand made a mistake in dropping the potential disciplinary proceedings.
Reay lodged an appeal in February but that has now been overturned, paving the way for disciplinary proceedings.
In a statement today Reay said he had already accounted for his actions and a further complaint hearing would be "an unjustifiable waste of focus and resource for ENZ and our engineering profession".
"The collapse of the CTV building could have been avoided, as the evidence to the royal commission showed. I did not cause that, and other engineers who reviewed it during and after it was built did not see the faults in it.
"That tragedy will continue to haunt me for the rest of my life - as I know it will many others. I have done everything within my reach to identify what happened and how the engineering profession can ensure that it will not happen again."
He said ENZ's and the profession's resources should focus on achieving better building standards and codes.
