 In the early 1990s he was also a founding member of the Petition of Fifty, a movement for democratic reform which included conservative military figures who had fallen out with Suharto and which for the first time in decades raised a real challenge to his rule.Along with other members of the group including Ali Sadikin and Hoegeng, Princen again found himself persona non-grata with the regime, although he joked to his visitors that by that time he was "too old to put in jail again".In 1996 he was involved in protests against Suharto's crackdown on the Indonesian Democratic Party (PRD).