Hearn has been opposed to the Barclays Premier League club moving to the stadium, which is a stones-throw from the Matchroom Stadium, home of npower League One outfit Orient.
"The LLDC have made a massive, massive mistake," he told Press Association Sport. "They are my lawyer's words and not mine, in as far as they have ignored their own rules so we are going to challenge that with a judicial review in the High Court."
He went on: "If we win then obviously discussions will be forced upon the LLDC and [mayor of London] Boris Johnson and everyone else and make sure they consider Leyton Orient.
"What does the world legacy really mean? I hear the word from politicians all the time and I don't think they can even spell the word.
"It is just a game. Well we are not in a game, we are in a fight for survival and we have to do everything available to us to continue the fight."
The drawn-out process to name an anchor tenant has long been questioned by Matchroom Sport chairman Hearn and he is still left with queries following the announcement
"It is a mess, the whole thing has been a mess for the last six years, horribly handled by lots of different people," he said.
"We are at the point where we are seeing if the club that is 750 yards away from the Olympic Park are being abused, ignored and sledge-hammered by a massive club.
"We think they have over-stretched their mark and the taxpayer will have something to say about it, but in the meantime we want to preserve the independence and existence of Leyton Orient Football Club."
- Sports & Recreation
- Barclays Premier League