Who defines the ranking?
Understanding the principles of CLP regulations

If you place a chemical product on the market, it is your responsibility to establish an appropriate classification for it. You must comply with the classification criteria set out in the CLP Regulation (Annex I and II), and seek out and consider all available relevant data on the hazards of the chemical in your assessment.

For more specific substances, you should also check that there is no harmonized classification at European level. In this case, the classification is listed in Annex VI of CLP, and must be applied throughout Europe. Harmonization applies in particular to CMR properties, respiratory sensitizers and biocidal or phytopharmaceutical substances (see Classifying a substance with a harmonized classification