A more thorough explanation:

The Feres doctrine is a legal rule that prevents members of the armed forces from suing the federal government for injuries that occur while they are on active duty. This means that if a soldier is hurt or killed while serving, they cannot sue the government for damages under the Federal Tort Claims Act (FTCA).

The Feres doctrine was established by the U.S. Supreme Court in a case called Feres v. United States. The court gave three reasons for the doctrine:

1. The FTCA requires private liability, which is not present in military service.
2. The relationship between the government and military personnel is "distinctively federal," and therefore not subject to local tort law.
3. Military personnel who have already received veterans' benefits for their injuries cannot also sue for damages under the FTCA.

For many years, the Feres doctrine prevented soldiers from seeking compensation for injuries caused by medical malpractice in military hospitals. However, in 2020, the National Defense Authorization Act created an exception to the Feres doctrine for cases of medical malpractice in military medical treatment facilities.

For example, if a soldier is injured during combat and believes that the government was responsible for their injuries, they cannot sue for damages under the FTCA because of the Feres doctrine. However, if the soldier is injured due to medical malpractice in a military hospital, they may be able to sue for damages under the new exception to the Feres doctrine.