Free blacks presented a challenge to the boundaries of white-dominated society. In many Southern states, particularly after Nat Turner's insurrection of 1831, they were denied the rights of citizens to assemble in groups, bear arms, learn to read and write, exercise free speech, or testify against white people in Court. After 1810, states made manumissions of slaves more difficult to obtain, in some states requiring an act of the legislature for each case of manumission. This sharply reduced the incidence of planters freeing slaves.