They did not "ban head scarves", they ruled that /if/ wearing religious symbols (and it gets interesting at necklaces with crosses) is not allowed, /then/ scarves fall under the rule, as well.

The ruling is more or less a nothingburger, because if you're against that restriction you're against the blanket ban in the first place, not so much against this specific interpretation. It's only interesting for legal doctrinal reasons.