Although it is always a good idea to remove all the snow from your vehicle before venturing out, it is not necessarily illegal in Ohio. In Michigan, it is another story. You can be fined. Flying snow and ice off other vehicles has caused damage and even death. Pennsylvania is another state where you can be fined for not clearing all the snow/ice off your car before taking it out on the roads.
So take a few extra minutes and push all that snow off before pissing off or injuring drivers behind you.