A Cook County judge is challenging a state law that imposes residency requirements on sitting judges who were elected from judicial subcircuits. Circuit Judge Patrick J. Sherlock was first appointed to the bench in March 2007, then elected in the 3rd Judicial Subcircuit in 2008. Voters from across the county chose to retain him in last month’s election. Now, Sherlock contends in a three-page complaint filed Friday that state law can’t require him to live within the boundaries of the 3rd Subcircuit, which …