The central figure in a scandal that badly tarnished the legacy of Chancellor Helmut Kohl, the father of German unification, arrived in Germany on Monday to face charges of bribery and tax evasion after a final attempt to delay his extradition from Canada failed.

The figure, Karlheinz Schreiber, an arms dealer and lobbyist, returned to Germany after a 10-year legal battle to remain in Canada, his adopted homeland.

Coming six weeks before national elections, Mr. Schreiber's arrival in Germany throws fresh light on an unwelcome chapter in the history of the conservative Christian Democratic Union, the party of Chancellor Angela Merkel, and its Bavarian affiliate, the Christian Social Union...