Eminent Domain

If a city or state government decides to build a freeway or redevelop a neighborhood, they have the power to condemn property and force people to move. Those people can bargain with the government over how much they should be paid for their property, but legally there is not much they can do if they want to stay.

This is called the power of eminent domain. The idea is that sometimes the government has to do something for the greater good that inconveniences a few people. We can disagree over whether building another freeway is "for the greater good," but most of us would agree that it can make things pretty difficult for the people who are asked to move.