[bilbo0s]

>if they take your land to build a road, they have to give you the fair market value of the land

Yeah, well, in Wisconsin under Walker, a lot of our farm families learned the hard way that this is not always the case. (Foxconn). It depends on how badly they want your land. But, yeah, it can be perfectly legal for the government not to pay you fair market value.

But to your central point, the government doesn't have to compensate you for anything in an emergency. That's why when criminals rob a bank or Walmart and then hide out in your home unbeknownst to you, the police are free to grenade the place. Perfectly legal for them to leave you the burning hulk of what used to be your house and say, "Don't thank us!" It was an emergency. (Or at least, they'll say it was.)