In Western legal traditions, democracy is inseparable from the rule of law, which presupposes the state to establish an effective and transparent judicial system that guarantees human rights and freedoms. The involvement of Lay Participation in the administration of justice (lay judges (mixed tribunal) or justices of the peace (magistrates) is one of the instruments for achieving this objective. The constitutions of the fourteen EU Member States, including Poland, oblige some Lay Participation in the administration of justice. However, the formulations of the norms in the constitutions, establishing Lay Participation in the administration of justice, differ. Based on the analysis of the Polish case, the article focuses on the question whether it would be sufficient to establish a relevant general provision in the Constitution, leaving the specification (form and extent of Lay Participation) to the legislator. The case of Poland has shown that the legislator can, without amending the Constitution, introduce other forms of Lay Participation (such as justices of the peace) or/and extend the extent of Lay Participation to judicial disciplinary cases when they are elected by the legislature; however, this poses a threat to the rule of law in Poland. Therefore, the article aims at discussing the impact of the Polish constitutional regulation of the Lay Participation on the violation of the rule of law.