Oklahoma Gov. Kevin Stitt has challenged the military's Covid-19 requirement.
CNN  — 

Oklahoma National Guard members must get vaccinated against Covid-19, a federal judge has ruled, denying a request from the state’s Republican governor and others to halt the military’s vaccine mandate.

The ruling Tuesday comes as GOP governors from six other states have also challenged the requirement.

Judge Stephen Friot from the Western District of Oklahoma denied Gov. Kevin Stitt’s request for an injunction against the vaccine mandate, writing in his ruling that Defense Department regulations “leave no doubt that the department’s vaccination protocols must, and do, apply as fully to the statutory reserve components (including the Guard) as to the active-duty forces.”

Like other Republican governors, Stitt had argued that he was the commander in chief of the state’s National Guard when it was not called up under federal orders.

In early November, he became the first governor to openly push back against the vaccination requirement, telling Defense Secretary Lloyd Austin in a letter that it “violates the personal freedoms” of some Guard members.

Earlier this month, six other Republican governors came out against the mandate, including Texas Gov. Greg Abbott, who said it was “unconscionable” that the military would threaten to withhold federal pay for unvaccinated members of the National Guard.

Governors from Wyoming, Alaska, Iowa, Mississippi and Nebraska also insisted the Pentagon does not have the authority to mandate the Covid-19 vaccine for state National Guard units.

As commander in chief of the state’s National Guard, Stitt asserted that he could refuse the military’s vaccine requirement. He ordered the adjutant general of the Oklahoma National Guard, Brig. Gen. Thomas Mancino, not to enforce the mandate, which requires all members of the National Guard to be vaccinated by the end of June 2022.

But the judge dismissed that argument, holding that members of the Guard must meet federal military readiness requirements, including medical vaccination requirements.

“However wide-ranging the command authority of the Governor and the Adjutant General may be within the four corners of their own state … it is unmistakably clear that the intent of Congress, as expressed in the text of its enactments, is that the Guard and its members will at all events be prepared, conformably to federal military standards, to be ordered into federal service, deploying alongside members of the active duty Army and Air Force, on little or no notice, anywhere in the world–which is exactly what the Oklahoma Guard and its members have done, with great distinction, on dozens of occasions,” Friot wrote.

Friot noted that Stitt had not objected to nine other vaccines required of all service members.

“The vaccine mandate to which the Governor objects is the one … intended to protect service members from the virus which has, in less than two years, killed more Americans than have been killed in action in all of the wars the United States has ever fought,” wrote Friot.

He pointed out that military vaccine mandates go back to the Revolutionary War, when then-Gen. George Washington mandated that troops in the Continental Army be inoculated against smallpox.

The judge urged the Defense Department to offer a grace period and “give every consideration” to unvaccinated Guard members “especially where, as appears to be the case here, the individual non-compliant Guard members did not have the benefit of well-informed leadership at the highest level of the Oklahoma Guard.”

CNN’s Tierney Sneed contributed to this report.