Twelve's the age for a Jewish woman to marry. It's also the age they have their Bat Mitzvah ceremony transitioning from 'girls' into 'women.' Because Islam bases so much of it's theology on Judaism, this sort of thing is to be expected.
Religious marriages are common (as distinct from civil marriages with a marriage license and such.) The FLDS do it frequently mixing in polygany.
It's an ongoing interesting legal question if a jusrisdiction allows freedom of religious practice, where is that line drawn? Obviously you don't then allow every little thing a religion may aspouse. But when some key component of most every religion is marriage, and you forbid the exercise of that religious rite on secular grounds, you're really taking a big bite out of the freedom to exercise religion. In the case of mainstream major faith like Islam, Christianity, Hinduism, etc. often times young marriage is going to be a thing. Lumping it in with statutory rape definitions is iffy at best.
Here in the US, while age of sexual consent is a variable from 15-18, the age to marry is often less and if married counts as an affirmative defense to a violation of the age of consent. As here in Missouri where the AoC is 17, but you can marry with parental consent at 15 (or younger with judicial consent.) And Rhode Island goes one step further recognizing the Jewish tradition of marrying first-cousins as an affirmative defense to the state's incest laws:
§ 15-1-4 Marriages of kindred allowed by Jewish religion. – The provisions of §§ 15-1-2 and 15-1-3 shall not extend to, or in any way affect, any marriage which shall be solemnized among the Jewish people, within the degrees of affinity or consanguinity allowed by their religion.
15-1-4
The marriage isn't contested in the Australian case. The article states he was charged with dozens of statutory rape charges after having had a sexual relationship with the young woman. On that count, he broke the law. But he was also married at the time (presumedly.) I'm not Australian, and I can't say I care a whole lot about how they define their marriage and age of consent laws. But on a strictly religion and the law level I think they made the wrong decision. If he did everything right by his reliigon and religious laws, then it's simply secular law vs religious law knocking heads together and as is often the case, secular law winning.
I condemn him for breaking local laws, but not the overall act.