"I repeat the declaration made a year ago, that 'while I remain in my present position I shall not attempt to retract or modify the emancipation proclamation, nor shall I return to slavery any person who is free by the terms of that proclamation, or by any of the Acts of Congress.' If the people should, by whatever mode or means, make it an Executive duty to re-enslave such persons, another, and not I, must be their instrument to perform it."