An extraordinary Sejm convened during a wartime mass mobilisation, with the entire nobility assembled in person under their land banners in a war camp (in loco campestri). The nobility who personally participated in the decisions usually gained majority in the camp assemblies. This represented a departure from the principle of representation. A camp Sejm certainly took place in Czerwińsk in July 1422, during the Polish army expedition against the Teutonic Order, when King Władysław Jagiełło issued a privilege of Czerwińsk (23 July 1422), in which he committed himself to minting the coin on the consent by the Royal Council, not to combine the office of starosta (mayor) with that of a land judge, to apply uniform law throughout the country, and to prohibit confiscation of property of noblemen without a valid court ruling. The provisions of the privilege undoubtedly represented forcing the king to make concessions, for which the fact of convening the Sejm in a war camp was certainly conducive.
In the 15th century, provincial camp assemblies were convened, which took place during the Thirteen Year War between Poland and the Teutonic Knights, which began in 1454. The first camp Sejm, the Wielkopolski Parliament, took place in September 1454 in a camp near Cerekwica, while the second camp parliament, the Małopolska Parliament, gethered in November 1454 in a war camp near Opoki. The nobility of Wielkopolska gathered at Cerekwica compelled the king to issue a privilege for the Wielkopolska lands (15 September 1454), in which, among other things, the king acknowledged not to call out mass mobilisation without a consent of the regional assemblies. Most of the provisions of the Cekekwica privilege were accommodated in the privileges issued by the king for other lands in Opoki, Nieszawa and Radzyń in November and December 1454. The first district privilege was of particular importance. It was issued in Nieszawa on 10 November 1454 for the Małopolska lands: Krakow, Sandomierz, Lublin, Radom, Wiślica, based on the demands of the Małopolska’s nobility drawn up in the Opoki camp (the Opockie petition), which were based on the privilege of Cerekwica previously granted to the nobility of Wielkopolska. On the basis of the district privilege for one of the Małopolska lands, a modified and supplemented district privilege for the all Wielkopolska lands was drawn up which removed the earlier Cerekwicki privilege. On the basis of the district privilege of Małopolska, a district privilege for the Ruthenian lands was issued on 10 December 1454 in Radzyń (certainly for the Chełm, Przemyśl and Sanok lands), and then for the Kujawy lands. The essential provisions of the privileges included the introduction of the need for the king to obtain the consent of the local assemblies to levy taxes and to call the mass mobilisation. The privileges issued during the camp assemblies in 1454, commonly referred to as the Nieszawa privileges (after the location where their final version was adopted), were unified in 1496 by king Jan Olbracht. Their provisions extended on all the lands of the Polish Crown, thus creating a universal Nieszawa privilege.
Another camp Sejm took place in 1520 in Bydgoszcz during a mass mobilisation for the Prussian war.The Sejm gathered in a camp circle and deliberations were held from 3 November to 7 December 1520, under a pressure exerted by an assembly of tens of thousands of noblemen. However, the Sejm passed a resolution to levy high taxes for the purpose of conducting the war campaign using mercenary troops, which could allow the king to disband the mass mobilisation.
See: M. Bobrzyński, O ustawodawstwie nieszawskim Kazimierza Jagiellończyka, Kraków 1873; A. Prochaska, Geneza i rozwój parlamentaryzmu za pierwszych Jagiellonów, Rozprawy Akademii Umiejętności, Wydział Historyczno-Filozoficzny, ser. II, vol. 13, Kraków 1899, p. 1-184; A. Prochaska, Przywilej czerwiński z 1422 r., „Przegląd Historyczny”, vol. 4, Warszawa 1907, p. 283-296; S. Roman, Zagadnienie prawomocności przywileju czerwińskiego z 1422 r., „Czasopismo Prawno-Historyczne”, vol. 11, 1959, fas. 1, p. 73-93; S. Roman, Przywileje nieszawskie, Wrocław 1957; Z. Wojciechowski, Zygmunt Stary (1506-1548), Warszawa 1946; Hejnosz W., Przywileje nieszawsko-radzyńskie dla ziem ruskich in: Studia historyczne ku czci Stanisława Kutrzeby, vol. I, Kraków 1938, p. 233-246.