The sons of corrupt former New South Wales minister Eddie Obeid have been ordered to co-operate with a consumer watchdog investigation into a mine licence deal.

Moses and Paul Obeid had appealed against a ruling that they must co-operate with the Australian Competition and Consumer Commission investigation relating the Mount Penny coal exploration licence.

The federal court today dismissed the appeal and ordered that they they must cooperate with the ACCC investigation into the exploration licence for the mine in the NSW Bylong Valley.

The ACCC is investigating if they were involved in cartel conduct during the 2009 tender process.

The investigation follows a report on the tender by the NSW Independent Commission Against Corruption (ICAC).

In 2013, ICAC found Eddie and Moses Obeid colluded with former mining minister Ian Macdonald, who granted the licence over the Obeids' family farm, Cherrydale Park.

ICAC found Mr Macdonald rigged the tender process and the Obeids stood to make millions of dollars from inside knowledge about it.

Five directors of Cascade Coal were also found to have acted corruptly by hiding the fact the Obeids were involved in the coal mining project.

In January 2014 former NSW premier Barry O'Farrell announced the licence would be cancelled.

ICAC also recommended that some of Eddie Obeid's business activities should be referred to authorities such as the Director of Public Prosecutions (DPP), the Crime Commission and the Tax Office.

As part of the investigation the watchdog issued notices under section 155 of the Competition and Consumer Act that required Paul and Moses Obeid to give evidence and produce documents in private ACCC examinations.

After throwing out their appeal today the Federal Court also ordered them to pay costs.

The Obeid brothers were not in court for the judgment.