Yes, a federal officer can arrest an innocent U.S. citizen, as mistakes happen, but they lack legal authority to target citizens without cause, particularly immigration agents who should only detain non-citizens, meaning such arrests are often unlawful and result in lawsuits, though agents can arrest citizens for committing federal crimes like aiding illegal immigration or other offenses they witness. While immigration officers (ICE) usually focus on non-citizens, other federal agencies like the FBI can arrest citizens for federal offenses, but all arrests must adhere to Fourth Amendment protections against unreasonable seizure,