This paper has three aims. The first is to explicate what kind of entity legal offices are and what their specific mode of existence amounts to. The second is to explain in virtue of what these offices can be said to be legal. Finally, third, to show the relevance of the actual use of legal offices for their existence. The main argument is that, ontologically, legal offices are best understood as immaterial institutional artifacts. This is because they can be created only if there is collective recognition of the relevant constitutive norms, which confer the status function of legal office, accompanied by the relevant deontic powers, and can continue to exist only for as long as this recognition is maintained. Furthermore, it is argued that so-called derived legal offices (e.g., the legislature and judiciary) are legal in virtue of the legal norms that constitute them, and the so-called original legal office (i.e., the constitution-maker) in virtue of the citizens’ norm of recognition (i.e., in virtue of its being collectively regarded as a legal office by the relevant community). Finally, the paper argues that as institutional artifacts, legal offices can be said to exist only on the condition that they are, at least initially, filled with officials actually carrying out the deontic powers accompanying the offices they hold and for as long as the initial citizens’ collective recognition of the original officials is not withdrawn.