ESSENDON coach James Hird has left the door ajar for an appeal to the High Court over his failed bid to have the ASADA doping case against 35 present and former Bombers players ruled unlawful.

Hird returned to Australia this week from New York, and admitted his unsuccessful Federal Court appeal against Justice John Middleton's finding that the joint ASADA-AFL investigation into Essendon's 2012 supplements program was lawful had been extremely costly.

"It has cost me a lot of money," he told Channel Seven on Monday.

"It's money we have to go out and find."

Hird said his appeal to the Federal Court was about the players' rights to a fair hearing, which he claimed had not been afforded them.

He said the players had been forced to give evidence without being given the confidentiality they were entitled to respect and without enjoying the same rights as the average Australian citizen.

Hird said he "reserved the right" to take the matter to the High Court.

The result of the AFL Anti-Doping Tribunal's inquiry into possible breaches of the League's anti-doping code is expected to be known within a month.