It appears that the from_obj method of the STIXCIQIdentity3_0 class and classes for child nodes of stix-ciqidentity:Specification do not call up to mixbox.entities.Entity.from_obj. mixbox.entities.Entity.from_obj emits a Entity.created.from_obj signal. stixmarx.parser.MarkingParser creates its set of entities to use for processing by subscribing its _handle_entity_created callback to the Entity.created.from_obj signal. As a result, since this signal is not sent for any entities of and including stix-ciqidentity:Specification, these entities are not marked by stixmarx. I'm creating this as an issue against python-stix because the CIQIdentity3_0Instance implementation is contained in this project.