"Federal law has now established that those seizures did not follow the letter of the law."

I think you have your cases confused. It was the Michigan Supreme Court that overruled their own ruling that allowed for the construction of the Poletown plant. But that only applied to state law. The US Supreme Court ruling in Kelo took a much more expansive view of eminent domain and would probably still allow a Poletown style condemnation, if done with federal power.