When the Pennsylvania National Guard, or any portion thereof, is ordered on active State duty by the Governor as Commander-in-Chief for the internal security of this Commonwealth or in case of disaster within this Commonwealth, the payment of the troops and all other expenses incident to such services will be made by the Adjutant General from funds obtained in the manner provided by law. If the Pennsylvania National Guard, or any portion thereof, shall be called into the active service of the United States by the President, all necessary expenses incident to the mobilization under such call shall be paid by the Adjutant General from funds as authorized by the Federal Government. The necessary transportation, supplies, equipment and necessary expenses incident to such Federal active duty within this Commonwealth or mobilization under the call of the President may be contracted for under direction of the Governor by the Adjutant General or other officer or officers designated for that purpose. The same shall be paid for by the Adjutant General from funds obtained as provided by law, except when such expenses are paid by the Federal Government.