The single-subject rule is a rule in the constitutional law of some jurisdictions that stipulates that some or all types of legislation may deal with only one main issue. One purpose is to avoid complexity in acts, to avoid any hidden provisions that legislators or voters may miss when reading the proposed law. Another is to prevent legislators attaching an unpopular provision ("rider") to an unrelated popular one, whether in the hope of sneaking the unpopular one through, or in the hope of causing the popular one to be rejected (a type of wrecking amendment).