Sovereign immunity renders the United States immune from suit unless it consents to be sued, which typically occurs through legislation like the Federal Tort Claims Act. However, even under such acts, certain exceptions apply where the government retains its immunity.
For example: Even though the FTCA allows for lawsuits for government negligence, if a postal truck driver negligently causes a car accident while delivering mail, sovereign immunity may not apply due to a specific statutory waiver under the FTCA.