Web scraping may be against the terms of use of some websites. The enforceability of these terms is unclear.[4] While outright duplication of original expression will in many cases be illegal, in the United States the courts ruled in Feist Publications v. Rural Telephone Service that duplication of facts is allowable. U.S. courts have acknowledged that users of “scrapers” or “robots” may be held liable for committing trespass to chattels,[5][6] which involves a computer system itself being considered personal property upon which the user of a scraper is trespassing. …