The Adjutant General shall have the power and authority to sell, at a fair market price, Illinois National Guard facilities and lands under his jurisdiction when in his judgment such facilities and lands are obsolete, inadequate, unusable or no longer required for Illinois National Guard purposes. All such sales shall be subject to the written approval of the Governor. Where the sale price of the facility exceeds 3.5 million dollars, and the facility is located in any county with a population of 1 million or more, the authorization of the General Assembly will be required for the sale of such facility.