THE CITY puts zoning or other restrictions on your property so that you can't use it as you had planned, and you sue. The court finds in your favor, saying the city exceeded its regulatory authority; its action went beyond legitimate regulation to become a taking of your land. It used to be that there were then two remedies. The city could acknowledge the taking and under the Fifth Amendment ("nor shall private property be taken for public use, without just compensation") pay you for it. Or it could rescind the regulation, in which case it would normally not have to pay you.

Now the Supreme Court in a bizarre decision -- Chief Justice William Rehnquist writing for a majority of six that included both himself and Antonin Scalia on the right, with William Brennan and Thurgood Marshall from the left -- has introduced a third possibility. Even if the city rescinds the regulation, it may have to compensate you for the down time during which you temporarily lost the use of your property.

The real estate industry was delighted, greeting the decision as simple justice long deferred. State and local government and environmental groups say, to the contrary, that it will chill the regulation of private property for public good, in that it adds to the risk if the regulatory authority oversteps its bounds. The court itself recognized this. It qualified its opinion somewhat, then acknowledged that even so "our present holding will undoubtedly lessen the freedom and flexibility of land-use planners. . . . But . . . many of the provisions of the Constitution are designed to limit the flexibility and freedom of governmental authorities, and the Just Compensation Clause . . . is one of them."

In the abstract, the court is right; if the government in regulating your use of your property goes so far as to take it, it should compensate you. As a practical matter the decision may indeed do some of the mischief the critics foresee, particularly because the law is so vague as to what constitutes a regulatory taking. The guidance is not much better than it was in 1922 when Justice Holmes wrote unhelpfully that a taking occurs "if regulation goes too far."

But that's tomorrow's problem. The majority noted that Justice Holmes also wrote years ago, "a strong public desire to improve the public condition is not enough to warrant achieving the desire by a shorter cut than the constitutional way of paying for the change." That seems fair.