The use of the capitol building and grounds shall be limited to departments of the state government and to state and national political organizations, and the keeper of public buildings and grounds shall not grant the use of either the capitol buildings or grounds for any other purposes, except that the Georgia Building Authority as keeper of public buildings and grounds is authorized to provide space in the capitol building for use as a vending stand, as described by Article 2 of Chapter 15 of Title 34, for the use of state officials and employees and their invited guests.