Iowa constitution
Article V
Section 18

Judges of the supreme court and district court shall receive salaries from the state, shall be members of the bar of the state and shall have such other qualifications as may be prescribed by law. Judges of the supreme court and district court shall be ineligible to any other office of the state while serving on said court and for two years thereafter, except that district judges shall be eligible to the office of supreme court judge. Other judicial officers shall be selected in such manner and shall have such tenure, compensation and other qualification as may be fixed by law. The general assembly shall prescribe mandatory retirement for judges of the supreme court and district court at a specified age and shall provide for adequate retirement compensation. Retired judges may be subject to special assignment to temporary judicial duties by the supreme court, as provided by law.