but failed on getting a vote before the end of the first session. Shortly thereafter, on September 17, 1861, the day the Maryland legislature was to reconvene, Lincoln imprisoned pro-Confederate members of the Maryland General Assembly without charges or hearings in further defiance of the Chief Justice's ruling. Thus, the legislative session had to be cancelled. On February 14, 1862, the war was firmly in progress and Lincoln ordered most prisoners released, putting an end to court challenges for the time being. He again suspended habeas corpus on his own authority in September that same year, however, in response to resistance to his calling up of the militia. Congressional suspension of habeas corpus When Congress met again in December 1862, the House of Representatives passed a bill indemnifying the president for his suspension of habeas corpus. The Senate amended the bill, and the compromise reported out of the conference committee altered it to remove the indemnity and to suspend habeas corpus on Congress's own authority. That bill, the Habeas Corpus Suspension Act, was signed into law March 3, 1863. Lincoln exercised his powers under it in September, suspending habeas corpus throughout the Union in any case involving prisoners of war, spies, traitors, or military personnel. The suspension of habeas corpus remained in effect until Andrew Johnson revoked it on December 1, 1865. General Ambrose E. Burnside had former-Congressman Clement Vallandigham arrested in May 1863 for continuing to express sympathy for the Confederate cause after having been warned to cease doing so. Vallandigham was tried by a military tribunal and sentenced to two years in a military prison. Lincoln quickly commuted his sentence to banishment to the Confederacy. Vallandigham appealed his sentence, arguing that the Enrollment Act did not authorize his trial by a military tribunal rather than in ordinary civilian courts, that he was not ordinarily subject to court martial, and that Gen. Burnside could not expand the jurisdiction of military courts on his own authority. The Supreme Court did not address the substance of Vallandigham's appeal, instead denying that it possessed the jurisdiction to review the proceedings of military tribunals without explicit congressional authorization. In 1864, Lambdin P. Milligan and four others were accused of planning to steal Union weapons and invade Union prisoner-of-war camps and were sentenced to hang by a military court. However, their execution was not set until May 1865, so they were able to argue