I'm not sure that states are actually required to have a National Guard contingent at all. They can have non-federalizable state forces, though in that case, they won't get federal funds for them.

https://en.wikipedia.org/wiki/State_defense_force

In the United States, state defense forces (SDFs) are military units that operate under the sole authority of a state government. State defense forces are authorized by state and federal law and are under the command of the governor of each state.[1][2][3]

State defense forces are distinct from their state's National Guard in that they cannot become federal entities. All state National Guard personnel (including the National Guard of the District of Columbia, the Commonwealth of Puerto Rico and the territories of Guam and the Virgin Islands) can be federalized under the National Defense Act Amendments of 1933 with the creation of the National Guard of the United States.