No. This recurring figure is extrapolated from a statement, old, and on the mode of the hypothesis, by Jacques Delors.
In fact, the true figure is around 20%. It is also necessary to distinguish, and from this point of view, a global figure does not make much sense. In some areas, where the sovereign states have decided to pool their policies, the EU has a strong legislative weight: this is the case for fisheries, the environment or agriculture.
But in many areas, as important as education, housing, social protection, an overwhelming portion of tax policy, defense or security, European influence is residual, not to say nil.
Finally, those who “make” the laws in Brussels are the MEPs (thus democratically elected) and also, and above all, the states: at the time of elaboration, the Council has a role of co-legislator (a sort of “super “Senate) and the Council is made up of national ministers; on the other hand, in the case of regulations and decisions (two types of European legal acts), States are, in addition, associated with their execution (their implementation), with a very strong weight. The EU can also issue directives: these are texts that give objectives to be attained (for example in the field of the very protective environmental laws) but it is the states that decide the instruments by which to achieve these objectives.