Article 2(1) in both the Ecodesign and Energy Labelling acts reads that: “(d) light-emitting parts contained in a light source from which these parts cannot be removed for verification as a light source” are not light sources. This definition is relevant for light strings/chains/strips: this light source cannot be dismantled up to the minimum light-emitting part, as the light-emitting part is not a light source: the light source in scope is the upper level, i.e. the entire light strings/chains/strips.
Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.