Member of the Bundestag
Kleinert was elected to the Bundestag in the 1969 federal election on the FDP's state list for Lower Saxony and was re-elected at each subsequent election until 1994. He sat from 20 October 1969 to 26 October 1998, from the 6th to the 13th legislative term.
From the end of 1969 he chaired the FDP parliamentary group's Working Group IV, which covered home affairs and law and, at times, education and the environment. His work there included data protection, bureaucracy and the volume of legislation. In his last term he was a full member of the Legal Affairs Committee, the Judicial Selection Committee and the committee that elects judges of the Federal Constitutional Court, and a deputy member of the Committee on Internal Affairs. He supported the repeal of Paragraph 175, the criminal provision against homosexual acts between men, and took part in drafting the reform of divorce law.
In July 1979, the Bundestag debated the abolition of the statute of limitations for murder, prompted by the approaching expiry of the limitation period for Nazi-era murders. Kleinert spoke for the majority of the FDP parliamentary group in favour of retaining the existing law. He argued that criminal justice should be kept separate from the country's responsibility for its history, that few unidentified perpetrators remained, and that the Majdanek trial had shown that fair trials were no longer possible after so long a period.
In May 1989, in a Bundestag debate on the conviction of the Memmingen gynaecologist Horst Theissen for illegal abortions, Kleinert criticised the conduct of the trial and described the women concerned as more victims than offenders.
On 23 November 1994, in the debate on Chancellor Helmut Kohl's government statement, Kleinert gave a short speech on legal and home-affairs policy while under the influence of alcohol. He spoke on whether electronic surveillance of private homes should be permitted, a question on which the FDP had not yet reached a decision, and his remarks drew repeated laughter from the opposition benches.
During the dispute over the German orthography reform of 1996, Kleinert, Norbert Geis and other members tabled a motion on German spelling, which the Bundestag debated on 18 April 1997.
In January 1998, Kleinert was one of the Legal Affairs Committee's rapporteurs on the amendment to Article 13 of the Basic Law that permitted electronic surveillance of private homes for criminal prosecution, and he took part in the cross-party negotiations on it for the FDP. In the Bundestag debate on 16 January 1998, he supported the amendment. He argued that its safeguards, including authorisation by a panel of judges, would limit surveillance to a small number of serious cases, and that the offices of lawyers and other professionals bound by confidentiality could not be fully exempted from surveillance.
