I have a lot of sympathy with the council's frustration and I suspect that this case is about highlighting an issue to consumers rather than using the law to force Sainsbury's to change their practices.
Ultimately the power to force supermarkets behaviour lies with us, the consumers. The problem is that we are hypocrites. I hear parents moan about the mountain of cardboard, plastic and bendy wires that comes with any and every toy we buy for our children. But would we be happy if the toy came in plain cardboard box with a picture on the front rather than a nice window with a chance to press the button which makes it go whizzzzzzz?
The Sainsbury's beef in question comes shrink wrapped, on a plastic tray, with a clear plastic covering and a cardboard sleeve. Would they sell as much if it was just shrink wrapped with an information sticker on the wrapping? They clearly believe not, or more significantly they know know that we won't because they've market tested alternatives.
We bemoan the loss of local shops, oppose to planning applications from supermarkets but the flock to them when they are opened. Whether packaging or planning, supermarkets follow our lead, they respond to our market demands, if we want them to change their behaviour we have to change ours.