My apologies Beatrix, I obviously wasn't being clear.
You said: The legal definition ought to follow any social definition
I answered: Fair point.
How long after it became apparent that raping your wife was actual rape, rather than just being a bit of a dick as a husband, did it become illegal to do so?
My point being that, as it took a fair while between the social definition of rape within marriage to tally with anything legislative, perhaps if we start educating young men and boys now that anything less than enthusiastic participation in sex probably suggests a lack of real consent now, in a similar fair while it will enter the legal canon.
If you are still unclear as to what I mean by enthusiastic, here are some synonyms: ardent, avid, eager, exuberant, fervent, keen, passionate, willing.
And here are some antonyms: apathetic, cold, cool, disinterested, frigid, indifferent, lethargic, unexcited, uninterested, unwilling.