The access rules capability of user module has been stripped down to a
  simple method for blocking IP addresses. E-mail and username restrictions
  are now available in a contributed module. IP address range blocking is
  no longer supported and should be done at the server level.

  This patch is partly motiviated by the fact that at the usability testing,
  it frequently came up that users went to "access rules" when trying to
  configure their site settings.