Kuwait's top court has ordered the dissolution of parliament and fresh elections.
The Constitutional Court made its ruling after throwing out opposition challenges to changes to the electoral system decreed by the emir.
Opposition politicians boycotted parliamentary elections in December in protest at the electoral rules.
Correspondents say the ruling is likely to herald fresh political volatility in the Gulf state.
It is the second time in a year that the court has ordered a dissolution of parliament. Last June it scrapped an opposition-dominated parliament, saying there had been flaws in the procedures that led to its election.
Kuwait's emir is now expected to set a new election day.
The voting rules upheld by the Constitutional Court allowed each voter to choose just one candidate at the ballot box, down from four previously.
They were decreed six weeks before December's poll, and led to mass protests.
Opponents said the new rules were designed to weaken the opposition, and that changes to the voting system should be agreed by parliament.
The government said the new system brought Kuwait into line with other countries.
Kuwait's parliament has lawmaking powers and can hold government ministers to account.
However, the emir has the final say in matters of state. He also chooses the prime minister, who in turn picks a cabinet, with members of the ruling al-Sabah family occupying the top posts.