The High Court has been asked to strike down retrospective laws passed by the NSW Parliament to validate a swath of corruption findings, in the latest front in a legal battle against the Independent Commission Against Corruption.

Lawyers for mining mogul Travers Duncan, who was found to have acted corruptly by concealing the involvement of the Obeid family in a coal tenement, claim the laws overstep parliament's powers under the Constitution.

Travers Duncan is asking the High Court to strike down laws validating ICAC findings. Credit:Brendan Esposito

The challenge comes a month after the High Court ruled the ICAC had no power to investigate Crown Prosecutor Margaret Cunneen, SC, in a decision that jeopardised findings against Mr Duncan and dozens of others.

The outcome will have major implications for targets of other ICAC inquiries.