The US government is suing Armstrong on behalf of the US Postal Service (USPS) and is seeking $100 million (AUD$130 million) in damages.
The US Postal Service, who sponsored Armstrong's team from 2000 to 2004, claimed it would not have done so if it had known the team was using banned substances and methods to win seven consecutive Tours de France, and alleged brand and reputational damage.
“Because the government has offered evidence that Armstrong withheld information about the team’s doping and use of (performance-enhancing drugs) and that the anti-doping provisions of the sponsorship agreements were material to USPS’s decision to continue the sponsorship and make payments under the agreements, the Court must deny Armstrong’s motion for summary judgment on this issue,” Cooper wrote in justifying the judgement.
Armstrong's attorneys have countered with the argument that the USPS did not suffer damages from the revelations and in fact received a positive return on its $32.3 million (AUD$42 million) sponsorship.
However, Cooper concluded that there was the possibility of brand damage to USPS and "the determination of damages must therefore be left to a jury" as he set the case for trial.
The lawsuit was originally filed in 2010 by Armstrong's former U.S. Postal Service teammate Floyd Landis, who stands to collect up to 25 per cent of the settlement as a whistleblower.
A trial date has not yet been set for the case.