Camp Lejeune Justice Act of 2020 This bill allows certain individuals to sue and recover damages for harm from exposure to contaminated water at Camp Lejeune in North Carolina between August 1, 1953, and December 31, 1987. This action is available only to individuals who were exposed to contaminated water for at least 30 days. In response to such a lawsuit, the U.S. government may not claim that it is immune from litigation based on an argument that the alleged harmful act or omission stemmed from (1) a federal government employee's execution of a statute or regulation, or (2) the federal government's exercise of its discretion. The bill also prohibits an individual who brings such an action from bringing a separate tort action against the United States based on the same harm.