Legal

• Federal preemption
  Federal preemption
  Federal preemption refers to the invalidation of US state law when it conflicts with Federal law.-Constitutional basis:According to the Supremacy Clause of the United States Constitution,...
  
  , displacement of U.S. state law by U.S. Federal law
• "Preemption" is also sometimes used in the United States to refer to the displacing effect state laws might have on ordinances enacted by municipalities, especially in the context of alcoholic beverage laws, gun laws
  Gun politics in the United States
  Gun politics in the United States refers to an ongoing political and social debate regarding both the restriction and availability of firearms within the United States. It has long been among the most controversial and intractable issues in American politics...
  
  , and in the area of FDA approved pharmaceuticals.
• Preemption, a type of land transfer in the United States, as in the Preemption Act of 1841
  Preemption Act of 1841
  The Preemption Act of 1841, also known as the Distributive Preemption Act , was a federal law approved on September 4, 1841. It was designed to "appropriate the proceeds of the sales of public lands.....
  
  
• Preemptive arrest
  Preemptive arrest
  A preemptive arrest is one in which a person is arrested prior to committing a crime. Preemptive arrests are sometimes viewed with suspicion as being contrary to the principles of a democracy. In the United States federal system, conspiracy to commit a crime in itself constitutes a crime, so an...
  
  
• Preemption Line
  Preemption Line
  The Preemption Line divides the Indian lands of western New York State awarded to New York from those awarded to Commonwealth of Massachusetts by the Treaty of Hartford of 1786...
  
  , the line that divided the Indian lands of western New York State, that had been awarded to New York from those that had been awarded to the Commonwealth of Massachusetts by the Treaty of Hartford of 1786
• Pre-emption right
  Pre-emption right
  A pre-emption right is a right to acquire certain property in preference to any other person. It comes from the Latin verb emo, emere, emi, emptum, to buy or purchase, plus the inseparable preposition pre, before. It usually refers to property newly coming into existence...
  
  s, the right of existing shareholders in a company to buy shares offered for sale before they are offered to the public
• FDA Preemption
  FDA Preemption
  FDA Preemption is the legal theory in the United States that exempts product manufacturers from tort claims regarding Food and Drug Administration approved products. FDA Preemption has been a highly contentious issue...
  
  , legal theory in the United States that exempts product manufacturers from tort claims regarding Food and Drug Administration approved products
• Pre-emption (Dominion Land Survey), a purchase right given to settlers under the 1872 Dominion Lands Act
  Dominion Lands Act
  The Dominion Lands Act was an 1872 Canadian law that aimed to encourage the settlement of Canada's Prairie provinces. It was closely based on the United States Homestead Act, setting conditions in which the western lands could be settled and their natural resources developed...
  
  

Other

• Preempt
  Preempt
  Preempt is a bid in contract bridge whose primary objectives are to thwart opponents ability to bid to their best contract, with some safety, and to fully describe one's hand to one's partner in a single bid. A preemptive bid is usually made by jumping, i.e. skipping one or more bidding levels...
  
  , a type of bid and a bidding tactic in contract bridge
• Preemption (computing)
  Preemption (computing)
  In computing, preemption is the act of temporarily interrupting a task being carried out by a computer system, without requiring its cooperation, and with the intention of resuming the task at a later time. Such a change is known as a context switch...
  
  , the interruption of a computer process without its cooperation in order to perform another task
• "Preemption", a form of broadcasting Blackout (broadcasting)
  Blackout (broadcasting)
  Blackout usually relates to the broadcasting of sports events, television programming, that is prohibited in a certain media market.The purpose is theoretically to generate more revenue by obliging certain actions from fans, either by making them buy tickets or watch other games on TV...
  
  
• Traffic signal preemption
  Traffic signal preemption
  Traffic signal preemption is a type of system that allows the normal operation of traffic lights to be preempted, often to assist emergency vehicles...
  
  
• Preemptive war
  Preemptive war
  A preemptive war is a war that is commenced in an attempt to repel or defeat a perceived inevitable offensive or invasion, or to gain a strategic advantage in an impending war before that threat materializes. It is a war which preemptively 'breaks the peace'. The term: 'preemptive war' is...