Sir,--A certain James O'Fallon is, as we are informed, undertaking to raise, organize and commission an army, of his own authority, and independent of that of the government, the object of which is, to go and possess themselves of lands which have never yet been granted by any authority, which the government admits to be legal, and with an avowed design to hold them by force against any power, foreign or domestic. As this will inevitably commit our whole nation in war with the Indian nations, and perhaps others, it cannot be permitted that all the inhabitants of the United States shall be involved in the calamities of war, and the blood of thousands of them be poured out, merely that a few adventurers may possess themselves of lands; nor can a well ordered government tolerate such an assumption of its sovereignty by unauthorized individuals. I send you herein the Attorney General's opinion of what may legally be done, with a desire that you proceed against the said O'Fallon according to law. It is not the wish, to extend the prosecution to other individuals, who may have given thoughtlessly into his unlawful proceeding. I enclose you a proclamation to this effect. But they may be assured, that if this undertaking be prosecuted, the whole force of the United States will be displayed to punish the transgression. I enclose you one of O'Fallon's commissions, signed, as is said, by himself. I have the honor to be, with great esteem, Sir, your most obedient humble servant. TO THE PRESIDENT OF THE UNITED STATES. Philadelphia, May 8, 1791.