Page 25 (f) the control of narcotics, hazardous and toxic wastes, nuclear materials, radioactive; (g) products or any other material used in the development or exploitation of nuclear energy. 20. Member States shall not so exercise the right to introduce or continue to execute the restrictions or prohibitions referred to in paragraph 3 of this Article as to stultify the free movement of goods envisaged in paragraph 1 of this Article. Article 42 Dumping Member States undertake to prohibit the practice of dumping goods within the Community. 21. For the purposes of this Article, "dumping" means the transfer of goods originating in a Member State to another Member State for sale: (a) at a price lower than the comparable price charged for similar goods in the Member States where such goods originate (due allowance being made for the differences in the conditions of sale or in taxation or for any other factors affecting the comparability of prices); and (b) under circumstances likely to prejudice the production of similar goods in that Member State. 22. In the event of alleged dumping the importing Member State shall appeal to Council to resolve the matter. 23. Council shall consider the issue and take appropriate measures to determine the causes of the dumping. Article 43 Most Favoured Nation Treatment Member States shall accord to one another in relation to trade between them the most favoured nation treatment. In no case shall tariff concessions granted to a third country by a Member State be more favourable than those applicable under this Treaty. 24. Any agreement between a Member State and a third country under which tariff concessions are granted, shall not derogate from the obligations of that Member State under this Treaty. 25. Copies of such agreements referred to in paragraph 2 of this Article shall be transmitted by the Member States which are parties to them, to the Executive Secretariat of the Community. Article 44 Internal Legislation Member States undertake not to enact legislation and/or make regulations which directly or indirectly discriminate against the same or like products of another Member State.