Natural law includes clear teachings about marriage (because marriage is a reality independent of positive law).— Josh Hochschild (@JoshHochschild) October 22, 2020
Natural law does not include clear teachings about "civil unions" (because civil unions are, by definition, defined by positive law).
Natural law includes clear teachings about what marriage is.— Josh Hochschild (@JoshHochschild) October 22, 2020
Natural law includes a general requirement that positive law support marriage.
Natural law does not determine precisely how positive law should support marriage.
But the Natural Law does have something to say about non-procreative sex acts. It also arguably has something to say about what status should be given to those who engage in such acts with members of the same-sex. After all, Thomists recognize that law as a teacher, and in this case, it is not merely about the "union" alone, but everything that is associated with it and is legitimized by it. The fact that SSA may be involuntary does not mean that mercy requires that we validate their lifestyle choices.