xmlimporter requires a new grouper session (is one being closed?)

Why is this check needed in XmlImporter.java?

GrouperSession staticSession = GrouperSession.staticGrouperSession(false);
if(staticSession==null)

{ staticSession = GrouperSession.start(SubjectFinder.findByIdentifier( rc.getProperty(XmlArgs.RC_SUBJ), true)); }

AuditEntry auditEntry = new AuditEntry(AuditTypeBuiltin.XML_IMPORT, "fileName",
rc.getProperty(XmlArgs.RC_IFILE), "subjectId", rc.getProperty(XmlArgs.RC_SUBJ));
auditEntry.setDescription("Imported xml: " + GrouperUtil.toStringForLog(args));
auditEntry.saveOrUpdate(true);
staticSession.stop();