I'm not aware of any mechanism the owners could use to stop the Bears. They'd have to vote on them leaving the market, but Hammond isn't them leaving the market.
About the only leverage I think is the NFL stadium loan. Would probably be about $300M loan. They could forgo that, but if Bears/Indiana want to make Hammond work I don't think that would be a hindrance (if other owners even cared, which I'm not sure they do).
I guess Super Bowl hosting is the only other variable. If they said "fine, but we're never approving a Super Bowl in freaking Hammond". Well that's pressure...