The "gag rule" against debates on slavery in congress started in 1835 began as a result of

The gag rule against debates on slavery in congress started in 1835 began as a result of petitions that were sent to Congress by the abolitionists. Due to petitions from abolitionists such as the American Anti-Slavery Society, the House passed a resolution that essentially deferred action on all petitions involving slavery

the passage of a strict fugitive slave law