While I appreciate your attempt at an example, maybe drink driving is a bit extreme. It's both deadly and illegal, and not a right or freedom that is being taken away, so not a great example of how someone may be coerced, or may be crossing a boundary.

Perhaps if you boiled it down to drinking.

One partner is a non-drinker. The relationship forms then the person who drinks is placed in a position where if they consume any alcohol, the person says they'll dump them. They try to have the discussion but get stonewalled. They reluctantly agree, but then months later are offered a beer at a couple of work functions and don't think much of it because its perfectly reasonable to have a beer. Then they find themselves in a position of having agreed to something unreasonable under the threat of being dumped, then having broken that whether unthinkingly or deliberately, and realising they'll get dumped of they're honest.

They're then in a position of lose/lose, either become a liar or get dumped because you had a beer with your workmates.

Again it's hard to come up with a great example at my end, we can poke holes in them all day long, but I hope that's a slightly better one?

A really interesting discussion nonetheless.