If a judge lacks a signed oath of office for their position, it could raise questions about their legal authority to act in that role. In most jurisdictions, an oath of office is a formal requirement for public officials, including judges, to affirm their commitment to uphold the law and perform their duties faithfully. The specifics depend on the legal system in question—whether it’s a state, federal, or other jurisdiction.
For example, in the United States, federal judges are required under Article VI of the Constitution to take an oath before performing their duties, and state judges typically have similar mandates under state laws or constitutions. Without a signed oath, a judge’s rulings or actions might be challenged as invalid due to a lack of proper swearing-in. Historically, courts have sometimes ruled that technical defects (like a missing or unsigned oath) don’t automatically void a judge’s actions if they were otherwise acting under color of law—so-called "de facto" authority—but this can vary case by case.