This is shaping up to be the century of consent. Confusing milkshake videos are one manifestation; restrictions on sex in marriage are a much older one.
Freedom, of course, has been a thing since at least the ancient Greeks.
For most of that time, though, the most attractive thing about freedom was that you had it (if you were lucky) and other people - slaves, women, lesser breeds - didn't. It was just another form of privilege, really.
People more or less stopped defending slavery in the 19th century, and in the 20th century women were gradually equipped with a judicious selection of rights.
The right to give or withhold consent was one of the toughest. The basic model for marital relationships was the ownership of property.
A woman belonged to her father until he passed her on to her husband.
In the Victorian Marriage Act of 1895, the only reference to the age of consent is the age of 21.
This didn't mean that all Australians waited till they were 21 to get hitched, though; it just meant they were under the control of their parents till then, and couldn't marry unless their parents gave permission.
Their own consent didn't hack it.
Not only was consent not enough to get you married, lack of consent wasn't enough to keep you safe.
In traditional English law, a husband forcing sex on his wife wasn't rape, because she'd consented, by the act of marriage, to any sex from that time forward, whether she wanted to or not; and that was law in parts of Australia till 1996.
The change, broadly, came about because people gave more weight to individual preferences and a good deal less weight to the institution of marriage.
It's hard for people growing up after the turn of this century to appreciate the power the concept of marriage held for our forebears, and that it holds in some other places even now.
It was a citadel of male power, and where law or ordinary morality came into conflict with that, it was law and morality that backed off. In particular, acts that would otherwise have been considered statutory rape were rendered legal by marriage.
Our tolerance for this kind of thing waned steadily over the 20th century, and since then we've moved firmly to requiring meaningful consent from people mature enough to know their own minds.
The age of marriage and the age of consent have drifted together at 16 (except in Alaska, for some reason, where you can still get married at 14). Children can't say "I do".
Which brings us to Walid Khodr. He met his wife in Australia when he was 19 and she was nine.
Her parents took the girl back to Lebanon in 2005, when she was 12, and she and Mr Khodr got married there (Lebanese law has since been changed to prevent such cases). She had her first child at 12, and has since had three more.
She's now living with them in Australia, and her husband wants to join her.
The Immigration Minister wants to stop him, basically because he thinks that someone who'd marry a 12-year-old is not a man of good character.
I agree with him (and it's so extraordinarily rare for me to agree with a minister for immigration that I feel obliged to flag it when it happens).
The minister said in his rejection: "If Mr Khodr's visa is granted and he came to live in Australia and obtained similar employment, I consider this could provide him with a platform to espouse his views regarding marriage and consummation of marriage with female children, including those under the age of 16." (When questioned by Immigration Department officials in 2014, Mr Khodr said that if one of his daughters wanted to get married, "as long as she reached puberty and it is 11, 12, 13, it is fine with me.")
The minister continued: "I find that the promulgation of these views by Mr Khodr has the potential to encourage others to engage in similar conduct, either in Australia, where it is prohibited by law, or abroad."
He described Mr Kohdr's behaviour as "repugnant to the expectations and standards of the Australian community."
The Federal Court has complicated things, though, by casting doubts on the minister's reasoning.
As the judge points out, the minister agrees that it's in Mr Khodr's children's best interests to have their father allowed into Australia (if only because there's otherwise a risk that they'll be taken back to Lebanon).
If Mr Khodr does proselytise for going overseas to get an underage marriage, that's already illegal in Australia, though only since 2013.
The future is here, as the science fiction writer William Gibson says, it's just not evenly distributed.
Denis Moriarty is group managing director of OurCommunity.com.au, a social enterprise helping Australia's 600,000 not-for-profits.