Recent environmental legislation emerging in Europe, such as IPPC Directive 96/61/EC, is driving changes ind the food industry.
Unlike some other treatements (irradiation and ionisation), ozone has no specific legislation. However, the following two rules apply:
Labeling Directive (2000/13) : The treatement must be indicated in the label - to not mislead the consumer.
Novel Food Regulation (258/97) : The treatement must have a premarket authorization for "novel foods".
The European Council of Ministers permits the ozone treatement of natural mineral water, but not spring water. That said, you can separate unstable elements (like iron, manganese ans sulfur compounds) from natural mineral water with ozone, which is superior than clorine.