That's basically a variant of eminent domain, but I suspect it would be a hard case to argue. Ukraine chose to use Starlink, and the US governments power to invoke eminent domain is based on the common good provided to the US public via the seized property. It's arguable whether the US public would see much if any value from the US government running Starlink unless they're going to start providing free service to US citizens. There's also the problem that there are plenty of other options that don't require seizing of property.