1. A computer-implemented method to define custodianship of content in an electronic discovery management system and maintain custodianship definitions at a content archive external to the electronic discovery management system, comprising: defining, in the electronic discovery management system, custodianship of content, wherein the content is stored in the content archive, wherein the custodianship specifies at least one parameter associating the content with a first custodian; and responsive to receiving a request to create a preservation plan for the content associated with the first custodian: modifying the request, in the electronic discovery management system and by operation of one or more computer processors, with the at least one parameter of the first custodian and at least one property of the content in the content archive; and responsive to receiving the modified request at the content archive: generating a query native to the content archive based on the modified request; executing the generated query at the content archive to obtain a result set comprising at least one content; upon determining, based on at least one of the result set and the modified request, that the content archive does not include an object representing the first custodian, creating, in the content archive, a custodian object representing the first custodian; associating the first custodian with the preservation plan; and placing the identified content on hold by associating the at least one content with the custodian object representing the first custodian.