The parliament may, when legislating with respect to a subject within the ambit of its powers, validly enact laws prescribing the rules of evidence and procedure to be observed in any legal proceedings, whether criminal or civil, arising in relation to that subject matter and may in particular cast the onus of proof upon either party to those proceedings: Williamson v. Ah On [18] ; Orient Steam Navigation Co. Ltd. v. Gleeson [19] ; and see also The Commonwealth v. Melbourne Harbour Trust Commissioners [20] . Of course, the parliament may not, by enacting legislation which purports to be merely procedural, extend the operation of its laws to subjects beyond its power; it cannot, in other words, expand the boundaries of its powers by its own enactments. For example, it could not validly provide that goods which had in fact originated in Australia should be deemed to have been imported, and that the customs legislation should accordingly apply to them. However, s. 233B (1) (ca), read in the light of s. 233B (1B), applies only to goods which have been imported into Australia, although the burden of proving that the goods were not imported lies on the person charged with the offence. Section 233B (1B) is an enactment of an evidentiary kind, and does no more than regulate the burden of proof, notwithstanding that if the fact in issue - that the goods were not imported - is established the person accused will have done nothing that could have been rendered unlawful by any enactment of the parliament. Section 233B (1) (ca) does not invalidly purport to apply to goods which in fact were not imported, for if it is proved, in the manner prescribed, that the goods were not imported, no offence is committed. The decision of this Court in Williamson v. Ah On [21] is in my judgment a very clear authority in favour of the validity of s. 233B (1) (ca) and s. 233B (1B). In that case the provisions of the Immigration Act Cth held to be validly made under s. 51 (xxvii.) and (xxxix.) of the Constitution operated in two ways now relevant - they placed on a person charged with being a prohibited immigrant the burden of proving that he was not an immigrant, and provided that the burden of proof should not be discharged unless (subject to an immaterial exception) the defendant in his personal evidence truly stated the name of the vessel by which he travelled to Australia and the date and place of his arrival. The provisions now under consideration do not go so far - they place the burden of proof on the person accused, but impose no limitation on the way in which the burden may be discharged. If Williamson v. Ah On was correctly decided, ss. 233B (1) (ca) and 233B (1B) should with stronger reason be held to be valid.