How to prevent navigation bar from being hidden, globally?

I know I can set some apps to not hide the navigation bar. But I would like to globally set that it should be shown **by default**. My Android is not rooted. Basically I want the old behaviour back in Android 4.0 (Ice Cream Sandwich) where it was not removable unless you root the device. However, I don't mind being able to allow it to hide the navigation bar on a per application basis.