Employees were always allowed to ignore after work email, but their bosses most likely would not have promoted them vs someone who responds on weekends.
As a CEO, I try to set a good example by not sending email after hours. I try not to reply to emails after hours, to make sure everyone knows that it's ok to not work after hours. Sometimes if I'm working on the weekend, I'll save the emails in drafts and send them out Monday morning, because while it's ok for me to work on my company on the weekends, I want to make sure my employees know that they are allowed to have a life too.
The only way you'll fix this on a large scale is by forcing that top down approach.
That being said, I'm not a huge fan of even more regulations, but I do see why they're sometimes necessary.