Democratic backsliding is a gradual process of elected governments increasing their powers, and at the same time, undermining the check-and-balance institutions of liberal democracy. Remarkably, such executive aggrandizement is often pursued through formal legislative acts jeopardizing fundamental rules of democracy, which ensures the persistence of ‘illiberal practices’ beyond a single government term. The illiberal legislation is usually developed and enacted stepwise over a longer period of time, so its full scope may escape the attention of media, opposition and academic observers. In this paper, we seek to systematically track illiberal legislative acts initiated by consecutive governments in the context of Central and Eastern Europe (CEE), thus exploring the long-term evolution of such legislation. For that purpose, we first elaborate on the concept of illiberal legislation, by identifying the key arenas which may be targeted and devising a coding scheme to assess the degree of change compared to a status quo document. In the second step, we apply this concept to legislation initiated by Polish governments in the period between 2005 and 2019, which includes both minority and majority populist governments led by the Right and Justice party (PiS) as well as mainstream governments led by the Civic Platform (PO). The analysis uncovers the nuanced patterns of illiberal legislation both across time and with respect to the distinct dimensions of liberal democracy. The paper constitutes the first step in a larger comparative project which aims to map illiberal legislation across CEE, and explain its initiation and success in the legislative process.