The is the upper house of the National Diet of Japan. The House of Representatives is the lower house. The House of Councillors is the successor to the pre-war House of Peers. If the two houses disagree on matters of the budget, treaties, or the nomination of the prime minister, the House of Representatives can insist on its decision. In other decisions, the House of Representatives can override a vote of the House of Councillors only by a two-thirds majority of members present.
The House of Councillors has 248 members who each serve six-year terms, two years longer than those of the House of Representatives. Councillors must be at least 30 years old, compared with 25 years old in the House of Representatives. The House of Councillors cannot be dissolved, and terms are staggered so that only half of its membership is up for election every three years. Of the 121 members subject to election each time, 73 are elected from 45 districts by single non-transferable vote (SNTV) and 48 are elected from a nationwide list by proportional representation (PR) with open lists.
Roles and responsibilities
The power of House of Councillors is very similar to the Canadian Senate or the Irish Seanad. In central issues, there is a "supremacy of the House of Representatives" (:ja:衆議院の優越, Shūgiin no yūetsu): In the election of the prime minister, in the ratification of international treaties and on passing the budget, a decision by the House of Representatives always overrides House of Councillors dissent. And only the lower house can pass votes of no-confidence against the cabinet. All other legislation requires either the approval by majorities in both houses, an agreement in the conference committee of both houses or an additional override vote by two-thirds majority in the House of Representatives. (No single party has ever won a two-thirds majority in the House of Representatives under the current constitution, although the LDP came close several times, as did the DPJ in 2009.) In other words: Controlling a majority in the House of Councillors and one third of the House of Representatives is enough for a united opposition to be able to block the passage of legislation. For certain important administrative nominations by the cabinet, the approval of both houses is required absolutely (although the laws containing this requirement could be changed by two-thirds lower house override as a "nuclear option"); and constitutional amendment proposals need two-thirds majorities in both the houses of the Diet to be submitted to the people in a national referendum.
One additional constitutional role of the House of Councillors is to serve as functioning fully elected emergency legislature on its own during lower house election campaigns: While the House of Representatives is dissolved, the National Diet can't be convened, and therefore no law can be passed in regular procedure; but in urgent cases requiring parliamentary action (e.g. election management, provisional budgets, disaster response), an emergency session (緊急集会, kinkyū shūkai) of the House of Councillors can still be invoked to take provisional decisions for the whole Diet. Such decisions will become invalid unless confirmed by the House of Representatives as soon as the whole Diet convenes again.
The basic stipulations on the role of the House of Councillors are subject of chapter IV of the constitution. Laws and rules containing more detailed provisions on parliamentary procedures and the relations between the two houses include the National Diet Law (国会法, Kokkai-hō), the conference committee regulations (両院協議会規程, ryōin-kyōgikai kitei), and the rules of each house (衆議院/参議院規則, Shūgiin/Sangiin kisoku).
Constitutional practice
In practice, governments often tried to ensure legislative majorities, either by forming coalition governments with safe legislative majorities in the first place or by negotiating with part of the opposition, or avoided to submit bills with no prospects of passage, so the House of Councillors rarely voted against the decisions reached by the lower house for much of postwar history: As the Liberal Democratic Party (LDP), founded in 1955, often held majorities in both houses or was sufficiently close to control both houses together with independents and micro-parties for a long period, inter-chamber disagreement was rare during most of the 1955 System.