In 1998 Papier, a member of the conservative CSU party, became Vice President and Chair of the First Senate of the Federal Constitutional Court of Germany.

When President of the Federal Constitutional Court of Germany Jutta Limbach retired from her position in 2002, Papier succeeded her.

He made an exception to this rule after the elections of 2005 when he implored the parties to work hard not to lose the trust of the German electorate.

From 2014 to 2016, Papier was part of an advisory board on internal reforms at Europe's largest automobile association ADAC.

[4] From 2017, Papier headed the so-called Limbach Commission (Advisory Commission on the return of cultural property seized as a result of Nazi persecution, especially Jewish property), a panel convened by the German government to give recommendations on restitution claims regarding art works stolen or purchased under duress by the Nazis.