Theresa Eminent Domain Lawyer, New York

A phrase used in property law to describe a right or duty that remains with a piece of property no matter who owns it. For example, the duty to allow a public beach access path across waterfront property would most likely pass from one owner of the property to the next.

Principles of international law so fundamental that no nation may ignore them or attempt to contract out of them through treaties. For example, genocide and participating in a slave trade are thought to be jus cogens.

(1) A legal principle that prevents a person from asserting or denying something in court that contradicts what has already been established as the truth. equitable estoppelA type of estoppel that bars a person from adopting a position in court that contradicts his or her past statements or actions when that contradictory stance would be unfair to another person who relied on the original position. For example, if a landlord agrees to allow a tenant to pay the rent ten days late for six months, it would be unfair to allow the landlord to bring a court action in the fourth month to evict the tenant for being a week late with the rent. The landlord would be estopped from asserting his right to evict the tenant for late payment of rent. Also known as estoppel in pais.estoppel by deedA type of estoppel that prevents a person from denying the truth of anything that he or she stated in a deed, especially regarding who has valid ownership of the property. For example, someone who grants a deed to real estate before he actually owns the property can't later go back and undo the sale for that reason if, say, the new owner strikes oil in the backyard.estoppel by silenceA type of estoppel that prevents a person from asserting something when she had both the duty and the opportunity to speak up earlier, and her silence put another person at a disadvantage. For example, Edwards' Roofing Company has the wrong address and begins ripping the roof from Betty's house by mistake. If Betty sees this but remains silent, she cannot wait until the new roof is installed and then refuse to pay, asserting that the work was done without her agreement.estoppel in paisSee equitable estoppel.promissory estoppelA type of estoppel that prevents a person who made a promise from reneging when someone else has reasonably relied on the promise and will suffer a loss if the promise is broken. For example, Forrest tells Antonio to go ahead and buy a boat without a motor, because he will sell Antonio an old boat motor at a very reasonable price. If Antonio relies on Forrest's promise and buys the motorless boat, Forrest cannot then deny his promise to sell John the motor at the agreed-upon price.(2) A legal doctrine that prevents the relitigation of facts or issues that were previously resolved in court. For example, Alvin loses control of his car and accidentally sideswipes several parked cars. When the first car owner sues Alvin for damages, the court determines that Alvin was legally drunk at the time of the accident. Alvin will not be able to deny this fact in subsequent lawsuits against him. This type of estoppel is most commonly called collateral estoppel.

A legally binding agreement involving two or more people or businesses (called parties) that sets forth what the parties will or will not do. Most contracts that can be carried out within one year can be either oral or written. Major exceptions include contracts involving the ownership of real estate and commercial contracts for goods worth $500 or more, which must be in writing to be enforceable. (See statute of frauds.) A contract is formed when competent parties -- usually adults of sound mind or business entities -- mutually agree to provide each other some benefit (called consideration), such as a promise to pay money in exchange for a promise to deliver specified goods or services or the actual delivery of those goods and services. A contract normally requires one party to make a reasonably detailed offer to do something -- including, typically, the price, time for performance and other essential terms and conditions -- and the other to accept without significant change. For example, if I offer to sell you ten roses for $5 to be delivered next Thursday and you say 'It's a deal,' we've made a valid contract. On the other hand, if one party fails to offer something of benefit to the other, there is no contract. For example, if Maria promises to fix Josh's car, there is no contract unless Josh promises something in return for Maria's services.

The taking of physical evidence or property by law enforcement officials. This runs the gamut from taking blood for a drug test to impounding a car used in a robbery. The police must generally obtain a search warrant, or court order, before they can seize personal property.

An old-fashioned term for a female executor--the person named in a will to handle the distribution of the deceased person's property. Now, whether male or female, this person is called either the executor or the personal representative.

A non-court procedure for resolving disputes using one or more neutral third parties -- called the arbitrator or arbitration panel. Arbitration uses rules of evidence and procedure that are less formal than those followed in trial courts, which usually leads to a faster, less-expensive resolution. There are many types of arbitration in common use: Binding arbitration is similar to a court proceeding in that the arbitrator has the power to impose a decision, although this is sometimes limited by agreement -- for example, in 'hi-lo arbitration' the parties may agree in advance to a maximum and minimum award. In non-binding arbitration, the arbitrator can recommend but not impose a decision. Many contracts -- including those imposed on customers by many financial and healthcare organizations -- require mandatory arbitration in the event of a dispute. This may be reasonable when the arbitrator really is neutral, but is justifiably criticized when the large company that writes the contract is able to influence the choice of the arbitrator.

A statement included in a patent application that describes the structure of an invention in precise and exact terms, using a long established formal style and precise terminology. Patent claims serve as a way for the U.S. Patent and Trademark Office (PTO) to determine whether an invention is patentable, and as a way for a court to determine whether a patent has been infringed. In concept, a patent claim marks the boundaries of the patent in the same way as the legal description in a deed specifies the boundaries of the property.