From the Ottawa Sun:

The Supreme Court of Canada is set to rule on whether spouse-swapping in public venues should be a criminal act. The ground-breaking case, which could set new standards for decency in Canadian society, stems from two Montreal "swingers" clubs charged with keeping a bawdy house.

One defendant, James Kouri, ran the Coeur a Corps bar, where couples could hook up by paying a $6 cover charge. Every half hour, a translucent black curtain automatically closed around the dance floor while people took part in, or watched, sex acts.

Kouri was convicted of keeping a common bawdy house and sentenced to pay fines of $500 on the first count and $5,000 on the second. He won acquittal from Quebec's top court, but the other club owner, Jean-Paul Labaye, lost his appeal.

Although there are similar prosecutions happening in the U.S. it's frequently a socialist (when you think about it you realize religion is frequently very socialist) mindset that drives this sort of prosecution.  The people are just cattle to be herded/controlled.  They don't have the brains to make decisions for themselves.  It's for the "greater good" that people are forbidden dominion over their own bodies.