Think your house is your castle? Our country’s Founders thought so. They put three provisions into the Bill of Rights to protect it. But last week, the Supreme Court said the government can take away your house just because it thinks someone else could make better use of your home or business than you can.

The justification? The Constitution does recognize that there are public needs, such as building roads, so vital the government must be able to take your land. It says the government may take property, but only for a “public use” and with “just compensation.”

The phrase at the center of last week’s case is “public use.” It’s an important phrase, because it’s supposed to mean that the government can only use force to take your property in order to do its job. The government, which is supposed to stop criminals from driving you off your land, isn’t supposed to get to force you off your land just because some official thinks someone else will put the land to “better” use.

I once brought ABC’s cameras to a neighborhood in New Rochelle, N.Y., that politicians decided to flatten to make room for an Ikea furniture outlet. The mayor boasted that a new store would replace a “blighted” neighborhood. Blighted? It was a perfectly nice group of homes and businesses.

I like Ikea stores. But let them build them on their own property. Why should homeowners be forced out? Why do the politicians get to decide? The people who lived in the neighborhood couldn’t believe what was happening to them. As one woman said, “What freedom do we have when we have businesses that will just come in and say, ‘Oh, you have to move’?” But businesses can’t force anyone to move. Only government gets to use force; Ikea was just the favored business that day. The government had decided that selling furniture was a “public use”: “urban renewal” that would be “good for the community.”

Said Dana Berliner, a lawyer for the libertarian law firm Institute for Justice, “It’s always what the ‘community’ wants. The ‘community’ wants to be more upscale. It figures it can get there by sacrificing some of its members, forcing them to move when they don’t want to.” Fortunately, the New Rochelle homeowners were able to keep their property. Ikea and the politicians backed down after the publicity.

Donald Trump wasn’t so easy. In the early Nineties, he wanted to expand one of his casinos in Atlantic City. Vera Coking was in the way. The elderly widow had lived in a house in Atlantic City for more than 30 years, and she didn’t want to move. So New Jersey’s Casino Reinvestment Development Authority sued to “acquire” Coking’s property.

It looked to me as though the government was robbing Coking to pay Trump. I confronted him about it: “In the old days,” I said, “big developers came in with thugs with clubs. Now you use lawyers. You go to court and you force people out.” He replied: “Other people maybe use thugs today. I don’t.” True enough. Trump didn’t send thugs after Coking; he sent the government. That’s worse. If he had sent thugs, Coking could have called the police. But when government forces you out of your home so that some other private person can pave it, whom are you going to call?

Trump wanted to turn Coking’s home into a parking lot. The court accepted the bureaucrats’ decision that the parking lot would be a “public use” but rejected Trump’s bid, saying Trump’s private benefit “overwhelmed” the public benefit. Justice Stevens, in his opinion for the Court last week, uses a similar notion when he claims that the purpose of taking your land to give it to some well-connected corporation must still be a public one, such as improving the economy; merely benefiting a company isn’t good enough.

But as Justice O’Connor pointed out in her dissent, if you can think of a more economically productive use for your home, you’d better worry. If a politician thinks of it, your castle may not be yours any longer.

Mr. Stossel is co-anchor of ABC News’s “20/20” and the author of “Give Me a Break,” just released in paperback.