1. which of these was nullified by the kansas-nebraska act? . missouri compromise. personal liberties laws. idea of popular sovereignty. crittenden compromise. 2. why was abolitionist john brown executed? . for his attempt to seize the arsenal at harpers ferry. for his midnight massacre. for his part in “bleeding kansas”. for beating charles sumner with a cane. 3. under the new fugitive slave act passed in 1850,. northerners could buy and sell slaves in washington, d. c. congress declared that slavery was morally wrong. popular sovereignty would decide the slave issue