Legislation adopted by parliament requires the assent of the Head of State
In some countries, the Constitution foresees that legislation adopted by parliament must be signed into law by the Head of State. If so, the Head of State may, for example, have the power to veto the legislation, return it to parliament, or submit it to another body such as a constitutional court.
Source
Legal documents that stipulate parliament's role.
Article 82 of the Constitution; according to the prevailing view in German jurisprudence, the Federal President can deny his assent only in cases, where the law wasn´t enacted in accordance with the provisions of the Constitution (formal unconstitutionality) or if the unconstitutionality with regard to content is evident.