Does a four-wheel drive vehicle require snow chains?

Some places make them mandatory, two that I know are Yosemite NP and British Columbia. In snowy conditions at Yosemite park entrance they will stop you at the gate and the directions range from please engage 4x4 to fit snow chains now. If you can't meet their requirements then you aren't coming in. On the border crossing from Alberta into BC on the trans Canada highway there are signs that say "snow chains required". Some vehicles can't take snow chains at all, Landrover Discovery being one example, the owners manual says "do not use chains" which gives you a problem visiting Yosemite in the winter. What do I think? High end snow tires and a modern off-road traction control system will do as well as or better than chains in most if not all conditions. A Discovery 2 with snow tires and no chains will easily go where an F-250 4x4 with standard tires and chains can't even move. So it depends.  more