Lance needs to write a check ASAP. I have read the lawsuit, but have not seen the arbitration award, settlement agreement or insurance contract. So, this is based on what the insurance company has alleged and media reports.
A settlement agreement is just a contract. Contracts can be set aside as being induced by fraud. It will depend on how tightly the settlement agreement was drafted. A claim of fraudulent inducement can be defeated by language in the contract disclaiming reliance on anything the fraudster did or said as an inducement to enter the agreement. Generally, waiver of reliance provisions are common and are generally enforceable. Absent such a provision, the contract can be set aside as being fraudulently induced.
The other issue is whether the res judicata prevents relitigation of the doping issue or whether this is a new claim based on the fact that LA was recently stripped of his titles. My understanding is that the insurance agreement requires a refund if LA is stripped of his titles. The issue in arbitration was whether the insurance company can withhold payment based on evidence of doping or whether the only way they could be relieved of having to pay is if LA was stripped of his titles. My understanding is that the arbitrators found that the insurance company could only withhold payment if LA was stripped of his titles. The arbitrators did not find that LA was clean and left that issue to UCI. So, now that LA has been stripped of his titles, he is obligated by the insurance agreement to refund the bonus money. This is a new claim and not relitigation of te issue of whether the insurance company could refuse payment based on their evidence of doping. It would be an absurd construction of the insurance contract if an athlete could bring a lawsuit seeking a declaration that the were clean, win the lawsuit and then be able to keep the prize money when they are stripped of their title. I think this is where LA is in big trouble.