282In that vein, according to the case-law, where it proves to be impossible to determine with certainty the existence or extent of the alleged risk because of the insufficiency, inconclusiveness or imprecision of the results of studies conducted, but the likelihood of real harm to public health persists should the risk materialise, the precautionary principle justifies the adoption of restrictive measures (see judgment 22 December 2010, Gowan Comércio Internacional e Serviços, C‑77/09, EU:C:2010:803, paragraph 76 and the case-law cited). When adopting a restrictive measure aimed at protecting the environment or human health, the competent institution in that regard is required to ensure a correct articulation between the precautionary principle and the principle of proportionality. That is the consequence of a reading of the case-law cited in paragraph 281 above in the light of the principle of proportionality which is enshrined in Article 5(4) TEU and which forms part of the general principles of EU law. That being the case, it must be held that the precautionary principle justifies the adoption of restrictive measures on condition that they are not only non-discriminatory and objective, but also proportionate (Opinion of Advocate General Bobek in Confédération paysanne and Others, C‑528/16, EU:C:2018:20, point 51).