In the meantime slavery was subjected to a series of destructive attacks in Congress, despite the views of some, who held that the institution was under constitutional protection. The passions and exigencies of the War, together with the humane motives from which the anti-slavery movement had sprung, did not leave these assaults without justification. In August, 1861, a law was enacted providing for the emancipation of negroes employed in military service against the government; in April, 1862, slavery was abolished in the District of Columbia; in May, army officers were forbidden to restore fugitives to their owners; in June slavery was prohibited in the territories; and in July an act was passed granting freedom to fugitives from disloyal masters that could find refuge with the Union forces. In the train of these measures, and in September of the same year in which most of them were enacted, President Lincoln issued his proclamation of warning to the South declaring that all persons held as slaves in the states continuing in rebellion on the 1st of January, 1863, should be "thenceforth and forever free." When the warning was carried into effect on the first day of the new year by the famous Proclamation of Emancipation, ownership of slave property in the border states was not abolished. The loyalty of these states was their protection against interference. As the Fugitive Slave Law was not yet repealed opportunity was still afforded to civil officers to enforce its provisions both north and south of Mason and Dixon's line. North of the line there was, however, no disposition to enforce the law. South of it wandering negroes were sometimes arrested by the civil authorities for the purpose of being returned to their masters. The following advertisement, printed two months and a half after the final proclamation went into effect, illustrates the method pursued in dealing with supposed fugitives:-- "There was committed to the jail in Warren County, Kentucky, as runaway slave, on the 29th September, 1862, a negro man calling himself Jo Miner. He says he is free, but has nothing to show to establish the fact. He is about thirty-five years of age, very dark copper color, about five feet eight inches high, and will weigh one hundred and fifty pounds. The owner can come forward, prove property, and pay charges, or he will be dealt with as the law requires. R. J. POTTER, J. W. C. March 16, 1863. 1 m."[836] [836] _Liberator_, May 1, 1863. Extract from the _Frankfort Commonwealth_, quoted by M. G. McDougall, _Fugitive Slaves_, p. 80.