EU Passport for Sale - A right of a Member State or a Violation of EU law.

Laura Johnson M noted ‘the act of exchanging a higher-value good (citizenship) for a lower value good (money) destroys the value of citizenship and corrodes public trust in that institution in a way that naturalization on other basis does not’, whereas, the value of EU citizenship, deriving from the national citizenship given, increases the value of the national citizenship. Numerous politicians describe the ‘buying of citizenship’ as a ‘back door entrance into the Union’.  

In his opinion Advocate general Maduro in the Case C-135/08, Janko Rottmann v Freistaat Bayern [2010] ECR I-1449 referred to the case of ‘mass naturalizations of third country nationals undertaken without consulting the other Member States’. Then, went a step further to mention the obligation that the Member States have under Article 4(3) of the Treaty on the European Union, which imposes an obligation on the Member States to loyal or sincere cooperation.

On the other hand, as Ayelet Shachar noted ‘the grant of citizenship is, as pure legal matter, a last bastion of sovereignty’

What is your opinion? Should the European Union through its institutions intervene and stop those actions by the Countries? Is so, does the EU has such power under the current legal framework? Is there a need for amendment of the law?