Single-subject rule

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 laws, to avoid any hidden 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).
Scope of a bill.
In English law, the long title of a bill or act of parliament states its purpose; this may enumerate multiple purposes, or end with a vague formula like "and for other purposes". A proposed amendment to a bill may be rejected if it is outside the scope defined in its long title; alternatively, the title may be amended to increase its scope. An omnibus bill covers a number of diverse or unrelated topics.
By country.
Australia.
Section 55 of the Constitution of Australia provides a single-subject rule for taxation legislation: "Laws imposing taxation shall deal only with the imposition of taxation, and any provision therein dealing with any other matter shall be of no effect". The same section also requires laws imposing taxation to "deal with one subject of taxation only" (except those relating to customs and excise).
Ireland.
The 1937 Constitution of Ireland states that "A Bill containing a proposal or proposals for the amendment of this Constitution shall not contain any other proposal". This was in contrast to the 1922 Constitution of the Irish Free State, which could be implicitly amended.
Sweden.
The Parliamentary Act () states that "proposals on different subjects may not be combined in one motion".
Switzerland.
In Swiss law, the "principle of the unity of the subject matter" (, , ) applies to federal popular initiatives and to parliamentary legislation that is subject to a referendum. It has been derived by the Swiss Federal Supreme Court from the provision in article 34, section 2 of the Swiss Federal Constitution which guarantees "the freedom of the citizen to form an opinion and to give genuine expression to his or her will" in the exercise of political rights. The Court has outlined the principle as follows:
United States.
The single subject rule exists in 43 state constitutions in the United States of America. 41 states apply the rule to all legislation, whereas Mississippi and Arkansas apply it only to appropriations bills.
For example, the constitution of Minnesota, Article IV, Section 17, requires that "No law shall embrace more than one subject, which shall be expressed in its title." Conversely, neither the U.S. Congress nor the U.S. Constitution has such a rule so riders which are completely unrelated to the main bill are commonplace. These amendments are often put into bills at the last minute, so that any representative who may read the legislation before actually voting on it will not have a chance to catch it. An effort is underway, however, to add a single subject amendment to the U.S. Constitution to apply a single subject rule to the Congress.
It has been charged that single-subject rules have been misused as a political or judicial measure to slow or nullify ballot initiatives. An example of accusation of misuse of this law occurred in Colorado when a former governor made a statement against a single-subject ruling. The rule can also result in overly narrow questions, that result in no substantial effects.
In July 2006, the Georgia Supreme Court ruled that a November 2004 amendment to the constitution of Georgia against same-sex marriage would be allowed to stand, despite also banning recognition of same-sex marriages done in other states, and banning civil unions. Additionally, voters in the referendum were told of only the same-sex marriage question, while the ballot failed to mention the other two issues, preventing voters from giving fully informed consent. A judge had previously ruled that voters had the right to decide the issue of civil unions separately, thus putting the two issues as one violated Georgia's single-subject rule.