natural right of killing the aggressor (the burglar)" and goes on to generalize in the following words: Not only was the doctrine considered to justify defense against neighbors and criminals, but any of the Crown's agents who attempted to enter without a proper warrant as well. Prohibitions of the Fourth Amendment to the United States Constitution share a common background with current castle doctrine laws. In 1841, The Preemption Act was passed to "appropriate the proceeds of the sales of public lands... and to grant 'pre-emption rights' to individuals" who were already living on federal lands (commonly referred to as "squatters"). During this same period, claim clubs sprung up all over the US advocating vigilance and the castle doctrine. This was in concurrence with the culture of manifest destiny which led to westward expansion and the American Indian Wars, the last of which ended by the 1920s. On the American frontier On the American frontier, the doctrine of no duty to retreat extended outside a residence. It asserted that a man in an altercation that he did not provoke was not obliged to flee from his attacker, but was free to stand his ground and defend himself. A state Supreme Court justice wrote in 1877, American West historian Richard M. Brown wrote that under the circumstances, for a man in the American West to flee under such circumstances would be cowardly and un-American. Legendary dentist and gambler Doc Holliday successfully used this defense when he shot Billy Allen as he entered a saloon. Holliday owed Allen $5 () which Allen wanted paid and had threatened Holliday. Although Allen was unarmed at the time, Holliday had received reports that Allen had been armed and looking for him earlier in the day. During the subsequent trial, Holliday asserted he was within his rights and the jury agreed. He was acquitted on March 28, 1885. Current position Today, the penal and civil forcible-entry laws of most American states forbid the use of force in the recovery of possession of land. At most the Castle Doctrine is an affirmative defense for individuals inevitably charged with criminal homicide, not a permission or pretext to commit homicide—which is generally unlawful. A minority of states permit individuals who have the right of immediate possession of land to use reasonable force to regain possession of that land, with Texas being the only state to allow the use of