The first Conscription Act, passed by the Confederate Congress on April 16, 1862, made all white males between the ages of eighteen and thirty-five eligible to be drafted into military service. (This was the first such draft in American history.) Although Confederate congressmen passed a variety of exemptions to maintain industrial and agricultural production, they initially refused to exempt overseers. Congressmen addressed this omission on October 11, 1862, by authorizing the exemption of one white man per plantation with twenty or more slaves, the so-called Twenty-Slave Law. The law also allowed an overseer exemption for two or more plantations within five miles of each other with collectively twenty or more slaves. The Twenty-Slave Law was in part a reaction to the preliminary Emancipation Proclamation , issued by U.S. president Abraham Lincoln on September 22, 1862. Confederates viewed the proclamation as Lincoln's attempt to foment slave rebellion. By their lights, the Twenty-Slave Law was necessary to ensure the productivity of the black population and to maintain the safety of the white population.

The Twenty-Slave Law created some resentment, especially among small farmers, who believed that the law benefited wealthy slaveholders at the expense of the common man. In response to the criticism, Confederate congressmen amended the Twenty-Slave Law on May 1, 1863, to apply only to overseers on plantations belonging solely to "a minor, a person of unsound mind, a femme sole [single woman], or a person absent from home in the military or naval service of the Confederacy." Congressmen required planters to swear an affidavit that they had been unable to secure an overseer not liable for military service and to pay five hundred dollars for the privilege. In addition, only men who had been overseers prior to April 16, 1862, on plantations that had not been divided since October 11, 1862, could qualify for exemptions under the Twenty-Slave Law.

Congressmen intended these latter provisions to prevent men from becoming overseers in order to evade conscription and to prevent planters from dividing their plantations to exempt additional overseers. On February 17, 1864, congressmen changed the requirement to fifteen able-bodied slaves and required planters with exempted overseers to deliver one hundred pounds of bacon or its equivalent for every slave on the plantation to the government and to sell his or her surplus to the government or to soldiers' families at government prices. In this way, congressmen ensured that the Confederate war effort benefited from the overseer exemptions.

The Twenty-Slave Law generated relatively little criticism in Virginia. In fact, many white Virginians viewed overseer exemptions as essential. Catherine Crittenden, a sixty-two-year-old widow in Culpeper County, requested that the governor excuse her overseer George Bowman from military service. She and her twenty-two-year-old daughter, Anna, had no protection as her son, Lieutenant Charles T. Crittenden, was already in Confederate service. "Not only for myself do I make this appeal … but for my neighbors, Mr. Bowman being the only overseer & nearly every man has volunteered." The result is "a thinly settled neighborhood, the farms being large, averaging 20 negroes to a farm, and not a man to keep order … Truly the condition of our neighborhood will be a lamentable one if we are left to the mercy of the negroes." The breakdown in plantation discipline as a result of the close proximity of Union troops and periodic food scarcities as a result of wartime devastation and military impressment muted criticism of the overseer exemptions in Virginia.