Prior to the rebellion, Virginia law had allowed education of slaves to read and write, and training of slaves in skilled trades. After the rebellion, and after a second conspiracy was discovered in 1802 among enslaved boatmen along the Appomattox and Roanoke rivers, the Virginia Assembly in 1808 banned hiring out of slaves and required freed blacks to leave the state within 12 months or face re-enslavement (1806). Free blacks had to petition the legislature to stay in the state, and were often aided in that goal by white friends or allies. In addition to the catalyst of Gabriel's Rebellion, the law against residency was prompted by the marked increase in population of free people of color in Virginia, as noted above in manumission of slaves after the American Revolution. The very existence of free blacks challenged the conditions of slave states!