Eversheds partner Owen Warnock said it currently fell outside existing legislation, giving some peace of mind to retailers and manufacturers that have adopted Guideline Daily Amounts for front of packs instead.
However, he warned: "The FSA may well still lobby for a traffic-light scheme to be introduced in European labelling law."
A spokeswoman for the FSA said it was in constant talks with the EU, which was fully aware of its pro-traffic-light stance.
Warnock added that the move by several food giants in recent months in favour of GDAs was a sign that the debate was only just beginning. "Many wish to win the debate by establishing labels based on GDAs in the minds of consumers.
"If that can be achieved then the traffic-light system will be weakened."
Last week, the FSA pipped the FDF's pro-GDA camp to the post with the first TV airing of traffic lights as part of its salt levels campaign.
The FDF, backed by several food giants, plans to launch a GDA ad campaign early next year, although Tesco has already run its own GDA campaign in recent months.