Shelter in place would mandate many people who are non essential to stop working to stop the spread. You can still go to the grocery store and pharmacies and go outside.
My work is still working as well as my wifes and many of my friends. My job is the only partially essential job as we need to keep fire systems functional in buildings.
^ this - means additional non food, non gas, non convenience stores need to shutdown and no parties.. going outside is ok, walking, jogging, etc
Government over reach? Yes. Martial law? Probably not, more likely the only thing cops would do differently is shutting down gatherings.