Page "Constitution of Poland" Paragraph 12

Until the death of Sigismund Augustus, the last king of the Jagiellonian dynasty, monarchs could only be elected from within the royal family.

However, starting from 1573, practically any Polish noble or foreigner of royal blood could become a Polish-Lithuanian monarch.

Every newly elected king was required sign two documents-the Pacta conventa (" agreed pacts ")-a confirmation of the king's pre-election promises, and Henrican articles ( artykuły henrykowskie, named after the first freely elected king, Henry of Valois ).

The latter document served as a virtual Polish constitution and contained the basic laws of the Commonwealth: