Liberal democratic institutions in the Philippines have been under attack. Under the Duterte administration (2016–22), Asia's oldest democracy saw abrupt reversals into authoritarian practices not experienced since the regime of Ferdinand Marcos Sr. (1965–86). These included extra-judicial killings as part of an ever-expanding war on drugs, the removal of the Supreme Court Chief Justice and legal threats against other high-ranking officials.

The use of impeachment procedures to threaten public officials is particularly noteworthy. When politicized, such threats can amount to a broad attack on liberal democracy, undermining the careful use of institutional checks and balances.

The use of impeachment as a political weapon is certainly not new, nor is it limited to the Philippines (Neumann 2007; Kim 2014; Hinojosa and Pérez- Liñán 2006). What is unprecedented, even by Philippine standards, was its prevalent use as a threat to remove officials critical of the administration. Within one year, former President Rodrigo Duterte and his allies within and outside Congress moved to impeach four high-ranking officials: former Vice-President Maria Leonor Robredo, former Commission on Elections (COMELEC) Chair Andres Bautista, former Supreme Court Chief Justice Maria Lourdes Sereno and former Ombudsman Conchita Carpio Morales. The eventual ouster of Sereno was widely seen as a serious setback for the rule of law (International Commission of Jurists 2018), while the concerted use of impeachment against other high-ranking officials and critical oversight institutions raised further concerns about a general illiberal turn in the Philippines (Bonoan and Dressel 2018; Thompson 2016).

The use of impeachment to undermine liberal institutions is somewhat paradoxical. Impeachment is the procedure by which selected high-ranking public officials can be removed from office if they are guilty of “culpable violation of the Constitution, treason, bribery, or other high crimes and misdemeanors, or betrayal of public trust” (Const., (1987), art. XI, § 2 (Phil.)).

Impeachment was originally established to ensure accountability—to check the powers of the monarchy or a strong executive—and only later applied to other high-ranking officials (Bernas 2011; Ellis 2005). Although inherently political (Broderick 1974), impeachment is entrusted to the legislature as an exceptional means to mitigate abuse of power. Impeachment requires high legal and procedural standards to counter destabilizing side effects (Kim 2014). It is, therefore, somewhat surprising to see how easily this extraordinary measure has been resorted to in the Philippines under Duterte.