Which of the following is not something a state government can do? decide how its legislature is organized decide what textbook its schools will use create a state navy regulate who can marry

State governments cannot create a state navy.

All defence policy, including the ability to have and maintain armed forces, is the responsibility of the national government.

However, there is such a thing as State defense forces (SDFs), which are military units operating under the authority of a state governor. Most states have laws allowing SDFs, and nearly half of them have such active forces. They are usually army forces, but there are also some air and naval units.