Constables in the United States
While Constables primarily serve the Courts, they belong to the executive branch of government.
Fourth branch of government
In politics of the United States, the fourth branch of government is an unofficial term referring to groups or institutions perceived variously as influencing or acting in the stead of the three branches of the US federal government defined in the Constitution of the United States (Legislative, Executive and Judicial). Views as to whether the influence is due or undue or the actions are for good or ill also vary.