Just as an addendum, the Church is clear in its present teaching about homosexual acts. I'm just pointing out that it appeals to natural law and NOT the Hebrew Scriptures to support its claim. In fact, the Church rarely appeals to Scripture at all when it formulates its teachings on sexual morality. The Church's teaching against homosexual acts are along the same lines as its teaching against masturbation and birth control -- that is, these things are forbidden because they dissociate sexual gratification/acts from their natural procreative ends.

If one endorses this paradigm and is consistent, then ANY act causing sexual gratification that does not involve the penis inside the vagina would be considered sinful. That chiefly includes oral sex among married heterosexual couples. Non-procreative by every stretch of the intellect. But we know that never happens. ;-)

Personally I find such appeals to nature to be flimsy. But this is the currently accepted paradigm among RCC theologians.