4. Section 4 of the Principal Act is amended by omitting from subsection (1) the definition of “Commonwealth vehicle” and substituting the following definition:“ ‘Commonwealth vehicle' means a motor vehicle that is owned by the Commonwealth and—
(a) bears a label attached to the windscreen that displays the letter ‘C' followed by a 7-pointed star, both in white against a blue background, and the word ‘COMCAR' in blue against a white background; or
(b) is, or is within a class of motor vehicles that is, declared by the Minister, by instrument published in the Gazette , to be a Commonwealth vehicle for the purposes of this Act;”.