Cards on the table here: I've worked part time since my first child was born, in 2003. For the first five years, I worked for a big pharma company, in a job share. I would have happily stayed in that job, had my husband not received a too-good-to-refuse job offer over an ocean. So, I quit that job and took up freelance writing, where editors set deadlines, but I determine when I work. Which means my part time career life has always had a predictable, regular schedule. (Income, of course, varies when one freelances, but I choose my own hours.)
However, for many part time workers, this is not the case at all. Managers provide completely unpredictable schedules (and often wait until the last minute to post said schedules), which makes things like child care almost impossible. Students can also find it difficult, as they need to work their schedules around their classes.
So, in steps the government. San Francisco, Vermont and Federal employees now have the "right to request" schedules that accommodate such things as school, child care, and elder care, according to the New York Times. Managers aren't required to give the requested schedule, but are required to listen to their employees.
Trust me when I say that this is a path that business owners do not want to go down. The next step will be requiring specific schedules for part time employees, and the last thing you want as a business owner is the government looking over your shoulder at ever schedule.
How to avoid this? Stop being a jerk. Yes, a jerk. Managers and business owners who jerk their employees around and value them less than the furniture, will get what they deserve in terms of more government regulation. There is no reason you can't give fairly regular schedules to your part time employees. Yes, I know that in some industries, work load can vary tremendously from time to time, and part time employees offer that flexibility you need to get the work done without having to pay people to sit around. Still, you can say, when there is work to be done on Tuesday, it will be done by Jane. Additionally, scheduling as far out as possible makes life easier for people to make arrangements.
If the government ends up stepping in, you'll lose that flexibility. As long as your part time workers are happy, they aren't going to complain. No complaints will (hopefully) mean no more intervention. You should be talking with your part time staff about their schedules. You should do your best to make schedules predictable. You should not be a jerk.
Another area the government will step in, and is doing so in SeaTac, Washington, is prohibiting employers from hiring additional part time workers when their current part time staff wants more hours. Now, it's certainly easier to give additional hours to current staff than it is to recruit and train new staff, but it kills your flexibility and your budget. Two part time employees can work at the same time when demand is high, but one full time employee can only work one shift at a time. Additionally, what happens when your part time employees demand more hours and push above the 30 hour limit and now you've got to provide health insurance? Killing that budget.
I fully support a business's right to do whatever they think is best for their company in regards to hiring and scheduling. However, what is right for your company is not treating your employees badly. I suspect that the people who brought about the new law in SeaTac weren't angry because they were consistently getting 25 hours a week and wanted 30, but who were getting 7 hours one week, 22, the next, and 13 the following, all while businesses were bringing on new people who were scheduled for 7 hours. Don't do that.
There are lots of horrible things managers do to part time people--demanding they come in for shifts they weren't scheduled for, giving them the worst hours, not providing reasonable advanced notice (schedule that begins Sunday is posted Saturday afternoon), and generally treating the employees as disposable.
Stop it. Do everything in your power to treat your employees--all of them--correctly. Not only will you have happier, more productive employees, you'll lessen the chances of the government stepping in and further limiting your ability to be flexible.