Sure will be awful hard to prove you needed a person more than 28 hrs...and were therefore in violation.
I can almost see a cottage industry of labor finders with a pool of fast foodians ready to work 20 hrs for one place and 20 hrs for another....they get their hours and the owners shed overhead....
It is a burden on the employee to have to report to two different locations to earn 40 hours pay. My girl friend lost her 40 hour / week job because she could not make it at 28 hours per week. But I guess the employer could not find reliable workers at 28 houra per week, so they rehired her at 40 hours. This law is causing extreme havoc for both employers and workers. It will make it a lot harder for many to find work.