It is the role of a revising chamber to scrutinise legislation that may have been drafted over-hastily in the lower house, and to suggest amendments that the lower house may nevertheless reject if it wishes to. An example is the British House of Lords, which under the Parliament Acts may not stop, but only delay bills. It is sometimes seen as having a special role of safeguarding the Constitution of the United Kingdom and important civil liberties against ill-considered change. By delaying but not vetoing legislation, an upper house may nevertheless defeat legislation: by giving the lower house the opportunity to reconsider, by preventing it from having sufficient time for a bill in the legislative schedule, or simply by embarrassing the other chamber into abandoning an unpopular measure.
Nevertheless, some states have long retained powerful upper houses. For example, the consent of the upper house to legislation may be necessary (though, as noted above, this seldom extends to budgetary measures). Constitutional arrangements of states with powerful upper houses usually include a means to resolve situations where the two houses are at odds with each other.
In recent times, Parliamentary systems have witnessed a trend towards weakening the powers of upper houses relative to their lower counterparts. Some upper houses have been abolished completely (see below); others have had their powers reduced by constitutional or legislative amendments. Also, conventions often exist that the upper house ought not to obstruct the business of government for frivolous or merely partisan reasons. These conventions have tended to harden with passage of time.
There is great variety in the way an upper house members are assembled. It can be directly or indirectly elected, appointed, selected through hereditary means, or a certain mixture of all theses systems. The German Bundesrat is quite unique as its members are members of the cabinets of the German states, in most cases the state premier and several ministers, they are just delegated and can be recalled anytime.In a very similar way the Council of the European Union, is composed by national ministers.
Many upper houses are not directly elected, but appointed: either by the head of government or in some other way. This is usually intended to produce a house of experts or otherwise distinguished citizens, who would not be returned in an election. For example, members of the Canadian Senate are appointed by the monarch on the direction of the prime minister.
However, it is also common that the upper house consist of delegates who are indirectly elected by state governments or local officials. For example, in the United States Senate until the passage of the Seventeenth Amendment in 1913.
In addition, the upper house of many nations is directly elected, but in different proportions to the lower house - for example, the Senates of Australia and the United States have a fixed number of elected representatives from each state, regardless of the population.
Many jurisdictions, such as Denmark, Sweden, Croatia, Peru, Venezuela, New Zealand, and most Canadian provinces, once possessed upper houses but abolished them to adopt unicameral systems. Newfoundland had a Legislative Council prior to joining Canada, as did Ontario when it was Upper Canada. Nebraska is the only state in the United States to have a unicameral legislature, which it achieved when it abolished its lower house in 1934.
The Australian state of Queensland also once had a legislative council before abolishing it in 1922; at this time members of the Legislative Council (the formal name of the state parliament) were not elected by the citizenry and so the council was found to be undemocratic and thus unconstitutional. As this was a purely internal matter, all other Australian states continue to have bicameral systems.