[jasonkester]

How do I tell my employer that my weekends are not for sale?

You could try selling him your weekends. And your nights.

Negotiate your position into a contract where you bill by the hour. That way he can have as many weekends as he likes. He can request you charge him for as many non-productive sleep-addled hours as there are in the week. Offer to "work" 24/7, so long as he's willing to pay.

The other way to pull this off is to get your entire team on board with the concept of "free time", "weekends", and "life". If everybody on your team were to slowly ramp their hours down to 40 per week, your employer would have but two choices: fire everybody or deal with it.

I've done both those things at various companies over the years. Both work nicely, provided you're prepared to land on the open market if things go south.