Can the European Union declare an individual persona non grata?

Question

From The Guardian (emphasis mine):

The European Parliament’s main political parties are making an unprecedented attempt to block Donald Trump’s likely choice as ambassador to the European Union (EU) from EU buildings, describing him as hostile and malevolent.

(...)

A letter from the leader of the Socialists and Democrats group, Gianni Pittella, describes Malloch’s statements as “shocking” and urges the EU institutions to treat him as a “persona non grata”. He writes: “Mr Malloch openly expressed himself to be in favour of the dissolution of the EU – to be ‘brought down as the Soviet Union’ – and wants to see the demise of the common currency within months, clearly show[ing] Mr Malloch’s hostility not only toward the European Union as such but also to our common values and principles.

(...)

“Therefore, the S&D Group is clear that Mr Malloch should not be accepted as an official representative to the EU and should be declared a ‘persona non grata’.”

Can the EU declare an individual as persona non grata? If so, who would be in power to do so? Could the European Parliament specifically declare that Mr. Malloch is banned from the EU, effectively blocking him as a potential ambassador to the EU?

(NB: Mr. Malloch is currently resident in the EU)

(Letter in full)

Answer 1

Declaring a diplomat a Persona non Grata is a standard act in international diplomacy. And it is not uncommon. Article 9 of the Vienna Convention on Diplomatic Relations, the "rulebook" of international diplomacy, explains what this means:

1. The receiving State may at any time and without having to explain its decision, notify the sending State that the head of the mission or any member of the diplomatic staff of the mission is persona non grata or that any other member of the staff of the mission is not acceptable. In any such case, the sending State shall, as appropriate, either recall the person concerned or terminate his functions with the mission. A person may be declared non grata or not acceptable before arriving in the territory of the receiving State.

2. If the sending State refuses or fails within a reasonable period to carry out its obligations under paragraph 1 of this Article, the receiving State may refuse to recognize the person concerned as a member of the mission.

There is just one caveat: The EU itself didn't sign the VCoDR. But all its members have. Also, the EU exchanges diplomatic missions with over a hundred different states, and these diplomatic exchanges generally play by the rules of the VCoDR. So one could reason that the VCoDR simply became customary law for the EU.

So yes, the EU can generally do that. But who in the EU can do it?

According to Article 15 of the Treaty of the European Union, external representation and foreign policy is generally the domain of the European Council, which consists of the government heads of the member states of the European Union. They do not necessarily need to ask the Parliament for permission to act in that domain. So the Council would consider the open letter by Gianni Pittella a suggestion they might or might not act upon.

Regarding Mr. Malloch's personal immigration status: Above reads "recall the person concerned or terminate his functions with the mission". If Mr. Malloch's function would be terminated (or rather not assigned in the first place), it would not have any effect on his immigration status. "Persona non Grata" only means that he needs to stay away from any diplomatic business and that he loses whatever rights he had due to diplomatic status. If his only legitimation for residing within the EU would have been diplomatic status, he would need to leave. But considering that he is already residing in the EU despite not being a member of any diplomatic mission, he apparently would not need diplomatic status to continue to do so.

Answer 2

Mr. Malloch before being appointed a head of a mission has to be approved/his candidacy needs an agrément from the European Commission, the Council of the European Union, the European External Action Service and the authorities of the Member States. European Parliament is not included. It's done in secrecy and the EU may deny without giving any reason. It's not the same as declaring someone persona nongrata. http://ec.europa.eu/dgs/secretariat_general/corps/index.cfm?go=vademecum.vademecum

Also, EU is not a state, has no territory, mission staff status is handled by the Belgian Government.