Un registro is obviously a "register" (when you mean the book in which information is recorded) or a "registry" (when you mean the office where the records are kept), but it has a second meaning--one that is important in el derecho procesal penal (criminal procedure).
Registro is also the word for "search" and the related verb registrar means "to search." Thus, for example, Article 18 of the Spanish Constitution states the following: El domicilio es inviolable. Ninguna entrada o registro podrá hacerse en él sin consentimiento del titular o resolución judicial, salvo en caso de flagrante delito.
An inexperienced translator may take this to mean that "no record may be made" in a private home, but what the provision really means is this: "Private homes are inviolable. They shall not be entered or searched without the owner's consent or a search warrant, except in cases where the criminal is caught in the act."
"Search warrant" (an important term is criminal procedure) is auto de registro in Spain. In other countries it is called orden de cateo (Mexico) and orden de allanamiento (Argentina).