Constables in the United States
While Constables primarily serve the Courts, they belong to the executive branch of government.
Federal judiciary of the United States
Under Article I of the federal Constitution, Congress also has the power to establish other tribunals, which are usually quite specialized, within the executive branch to assist the President in the execution of his or her powers. Judges who staff them normally serve terms of fixed duration, as do magistrate judges who assist Article III judges. Judges in Article I tribunals attached to executive branch agencies are referred to as administrative law judges (ALJs) and are generally considered to be part of the executive branch even though they exercise quasi-judicial powers. With limited exceptions, they cannot render final judgments in cases involving life, liberty, and private property rights, but may make preliminary rulings subject to review by an Article III judge.The Supreme Court has interpreted the Constitution as placing some additional restrictions on the federal courts. For example, the doctrines of mootness, ripeness, and standing prohibit district courts from issuing advisory opinions. Other doctrines, such as the abstention doctrine and the "Rooker-Feldman" doctrine limit the power of lower federal courts to disturb rulings made by state courts. The "Erie" doctrine requires federal courts to apply substantive state law to claims arising from state law (which may be heard in federal courts under supplemental or diversity jurisdiction). In difficult cases, the federal courts must either guess as to how a court of that state would decide the issue or, if that state accepts certified questions from federal courts when state law is unclear or uncertain, ask an appellate court of that state to decide the issue.