"No Department of Defense funding may be allocated for payment of duties performed under title 32 for members of the National Guard who do not comply with Department of Defense COVID-19 vaccination requirements," Austin said in the memorandum on Tuesday.
National Guardsmen opposing vaccination will also be marked absent without cause from drills and training, which means they will not get credit for service time, the memorandum said.
The new policy must be imposed no later than December 6, the memorandum said, adding that vaccination is essential to the health and readiness of the US armed forces.
There are more than 400,000 Americans serving in the National Guard.