The entire purpose of the National Guard, formerly known as Militias at the time of writing the Bill of Rights, was to protect and defend We the People from a tyrannical government. Enforcing xtofascism is the complete opposite of the original intention. The NG should be stopping ICE instead.
They have the right to refuse unlawful orders.
As a veteran, I took an oath to defend the constitution against all enemies, both foreign and domestic. The oath is quite explicit on that responsibility not ending if the people harming the constitution also live here.
You are correct that our oath to uphold the Constitution explicitly states defending against All enemies, both Domestic and foreign. Xtofascist MAGAt's fall into the domestic enemy category.