While, in justifying the disallowance of the ACT legislation, the Attorney-General stressed — and mischaracterized — the constitutional, legal, question, the Prime Minister emphasised the moral, normative, question: marriage had to be preserved as a heterosexual institution.The Greens took issue with this justification for disallowing the Act: 'The only explanation offered is that civil unions would "undermine" marriage, but they cannot explain how this would actually happen.' Indeed, Labor, as we have seen, was apparently prepared to support the legislation partly because it believed it did not impact on marriage as a heterosexual institution.
The government and the opposition disagreed about the proposition that recognising same-sex civil unions would have the effect of undermining heterosexual marriage. They both took for granted one point, however: that marriage should remain heterosexual, apparently because they believe that the value of the institution is somehow bound up with its heterosexual character.Whether or not the value of marriage is inseparable from its heterosexuality is not only the logically antecedent question in the debate over civil unions, but also a fundamental moral question relevant to the issue of the legal recognition of SSM. As we have seen, assuming that CM includes SSM, the Commonwealth could use the marriage power to render inoperative State SSM statutes. But should it?
Given the paucity, tautological character and lack of sophistication of the justifications provided by the government for keeping marriage heterosexual, one has to look elsewhere in order to make sense of the proposition that the value of the institution is somehow inseparable from its heterosexual character. New Natural Law theory provides the most elaborate theory of marriage among those seeking to justify the value of the institution in a way that poses the different sex of the spouses as central to what counts as (valuable) marriage. Further, New Natural Law theorists themselves have claimed that their 'account [of marriage] also articulates thoughts which have historically been implicit in the judgements of many non-philosophical people'. The plausibility of this claim seems to be borne out by the similarities between the arguments made in defence of heterosexual marriage by Finnis (the foremost New Natural Law exponent) and those provided by Family First Senator Fielding (Vic) when enthusing about marriage during the debates on the motion to disallow the Governor-General’s disallowance. It seems also significant that, although the Prime Minister, in defending the disallowance of the ACT law, did not expressly use Finnis's children and sexual complementarity arguments (analysed below), similar arguments have figured as part of his rhetorical repertoire when defending other regressive policy proposals on the ground of sexuality or gender. Indeed, with such people in Howard's Ministry as conservative Catholic Tony Abbott, and given Finnis's own position of prominence within high profile international Catholic networks and circles, it would be surprising if New Natural Law Theory had not played a role in directly informing the government's action on the ACT legislation.
In addition to informing executive and legislative initiatives of the sort described in this paper, normative arguments for or against the necessary heterosexuality of marriage such as those advanced by New Natural Law Theory are likely to figure among the considerations that Courts might take into account when attempting to determine the constitutional meaning of 'marriage'. This is not so much because the courts would necessarily try to fill that constitutional term with a meaning that happened to support their own convictions on what marriage should be about; rather, it is because a consideration of contemporary debates about what marriage should mean is relevant to establishing what is the contemporary denotation of the term, and may even assist us in determining what is the stable connotation of that term across time. In other words, the constitutional questions considered in the first half of this article are more than just accidentally connected with the normative questions analysed in the second part: the connection is not just at the level of contingent political discourse (both constitutional and normative arguments having been adduced to defend, for example, the disallowance of the ACT legislation), but operates at a deeper level, normative questions being partly relevant to answering the constitutional questions
In this sense, D must be the correct answer.