On foreign and military policy, Lincoln spoke against the Mexican–American War, which he imputed to President James K. Polk's desire for 'military glory—that attractive rainbow, that rises in showers of blood.' His legal reputation gave rise to the nickname 'Honest Abe'.Lincoln argued in an 1858 criminal trial, defending William 'Duff' Armstrong, who was on trial for the murder of James Preston Metzker. The case is famous for Lincoln's use of a fact established by judicial notice to challenge the credibility of an eyewitness. In July, the Confiscation Act of 1862 was enacted, providing court procedures to free the slaves of those convicted of aiding the rebellion; Lincoln approved the bill despite his belief that it was unconstitutional. He felt such action could be taken only within the war powers of the Commander-in-Chief, which he planned to exercise. Lincoln at this time reviewed a draft of the Emancipation Proclamation with his cabinet.Privately, Lincoln concluded that the Confederacy's slave base had to be eliminated.