_Protection Against Invasion._--It is also made the duty of the national government to protect the states against invasion. This is right and proper, since the states are forbidden by the Constitution to keep ships of war or troops in times of peace. _Protection Against Domestic Violence._--Again, it is made the duty of the national government to protect the people of the states against domestic violence arising from insurrection or riots, _provided_ that application has been made by the proper state authorities. The purpose of this proviso is to remove the temptation to federal interference in state affairs for political or other reasons against the wishes of the people of the state. The ordinary procedure for the suppression of a local disturbance is for the sheriff of the county, or the mayor of the city, to make use of the local police, and if necessary he may call upon the citizens to come to his aid. If this is not effective, the governor may be called upon to order out the state militia for the suppression of the riot. If, however, the riot should spread and assume such proportions that the power of the state and local authorities is insufficient, it becomes the right and duty of the governor, or the legislature if it be in session, to call on the President of the United States for the assistance of national troops. If in the President's judgment the situation is one which warrants federal intervention, he sends a detachment of troops from a near-by military post to restore order. Many times in our history federal troops have been used to put down riots where the state authorities had shown themselves incapable of maintaining order; two recent examples being in connection with strikes among the miners of Nevada in 1907, and of Colorado in 1914. Ordinarily the President has no lawful right to interpose in the affairs of the state by the employment of troops until he has received an application from the governor or the legislature, but if the disturbance is one which interferes with the operations of the national government or with the movement of interstate commerce, the President may intervene whenever in his opinion the situation calls for federal action. Thus during the Chicago strike riots of 1894, President Cleveland ordered a detachment of federal troops to that city against the protests of the governor, upon being assured that the strikers were interfering with the movement of the mails and with the conduct of interstate commerce and were also disregarding the writs and processes of the United States courts. The interference of the President was criticized by some persons, but the great body of citizens approved his course, and the United States Supreme Court upheld the validity of his action.