Defense Secretary Lloyd Austin has ordered that all members of the National Guard and Reserve must receive Covid vaccines or face loss of pay and being marked absent without cause from drills and training, according to a copy of a memo obtained by NBC News. .

The mandate extended to all service members on active duty or in the Ready Reserve, including the National Guard.

Kevin Stitt of Oklahoma wrote a letter to Austin, asking him to rescind the vaccine mandate for members of the Oklahoma National Guard.

What remained unclear, however, was how the Pentagon planned to enforce the mandate for members of the National Guard while they are on state duty. Most of the time, including when they are training, members are on state duty and answer to their governor.

According to the memo, which was sent to the service secretaries, the chairman of the Joint Chiefs of Staff, the head of Pentagon personnel, and the highest-ranking officer in the National Guard, known as the chief of the National Guard bureau, members must be fully vaccinated in order to participate in drills and training.