VMS Help CMS, MODIFY, GROUP, Qualifiers, /NOREAD_ONLY  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Establishes or alters the read-only attribute of a group. To
    change the characteristics of a READ_ONLY group, you must set
    the class to NOREAD_ONLY. NOREAD_ONLY is the default attribute of
    a group when it is created with the CREATE GROUP command.