Sejm

Historically established in 1493 as a tripartite (king, nobility, senate) body, it nevertheless was primarily dedicated to the maintenance of status quo, which was at the time power in the hands of a small percentage of the population (aka an oligarchy). As such it was surprisingly powerful, rivaling the king in powers, as votes had to be unanimous (i.e., a single person could veto any proposal). This also crippled it for the larger part of the 17th century, and led to its downfall in the 18th.

In the 2nd half of the 18th century there were attempts to repair the Sejm. The Constitution of May 3, 1791 was supposed to introduce a modern, two house system which would include not only the nobility but also the commons, and which would rely on majority voting to establish laws. This never truly came into play as, due to the partitioning of Poland the country ceased to exist.

There was a brief period of excitement in what's called the inter-war period (1919-1939). Immediately after regaining independence in January 1919 a new Legislative Sejm was elected democratically. It established a so called Little Constitution which made Poland into a republic and gave it parliamentary rule. The 1921 March Constitution strengthened the Sejm, making it the central ruling body. After the May 1926 coup attempted by Józef Piłsudski, the Sejm's role diminished and fell under the rule of the President - this was ratified by the April Constitution of 1935.

For 40 years after World War II, the Sejm was basically a powerless puppet; true power was held by the Soviet-created PZPR (Polish United Workers' Party).

After the Round Table elections in June 1989, the Sejm and the Senate became the center of political activity. The following elections in 1991 and 1993 allowed the Sejm to become the representative body that it was supposed to be, and together they form the legislative body today.

Currently the Sejm is composed of 460 representatives chosen by popular vote. Each Sejm lasts 4 years; each session is started afresh (i.e. outstanding issues from the previous Sejm do not carry over).

Besides legislating, Sejm also controls some aspects of the government. It elects several judicial officials and spokesmen, and can initiate motions to remove ministers and even the head of Cabinet.

Finally, the Sejm decides when to declare martial law and when to allow the government to issue decrees as laws. Together with the Senate they have the power to decide a new constitution.

Elections to the Sejm are called by the president; the president may dissolve the Sejm as mandated by the constitution. The Sejm may also dissolve itself.

Source:
http://www.sejm.gov.pl
http://wiem.onet.pl/wiem/008aa2.html
Messr. Gorgonzola for oligarchy :)