On May 27, 1863, Chief Justice Roger B. Taney of Maryland issued Ex parte Merryman, challenging the authority of President Abraham Lincoln to suspend the writ of habeas corpus in Maryland, the legal procedure that prevents the government from holding an individual indefinitely without showing cause.
Two days earlier, John Merryman, a vocal secessionist, had been arrested in Cockeysville. Although military officials continued to arrest suspected Southern sympathizers, the incident led to a softening of the policy.