What EU or German law allegedly prevents a foreign king to rule his country from the German soil?

Question

Recently, Germany’s FM Heiko Maas has said that HRM Thai King Maha Vajiralongkorn should not be conducting politics while staying in Germany:

"We have made it clear that politics concerning Thailand should not be conducted from German soil."

German MP Schmidt asked (highlight mine):

“Why does the German government tolerate this extremely unusual - and in my opinion illegal - behaviour of a foreign head of state conducting politics on German soil?”

Why could this be illegal at all, from Germany's view? If there any specific EU/German law preventing a foreign king to rule his country from German soil?

---

Context:

The Thai Constitution seems to have provisions allowing HRM exercise powers while being abroad. The absence of the King during the COVID epidemic has, indeed, triggered protests in Thailand calling to amend the Constitution, but (1) it is clearly in agreement with the Thai Constitution before any amendments have been ratified, and (2) it is about Thai Constitution, not the EU or German's.

Also, I'm aware that the EU and Thailand have tensions after the the 2014 military coup. But then again, it's not about members of a military junta (who can be accused of being undemocratic, for example), but about a ruling monarch of a recognized state.

Answer 1

This took a bit of searching. It has nothing to do with the fact that the Thai king is investigated because he cheated on his taxes, although that is an amusing side note (as a permanent resident of Bavaria, he allegedly owes the Bavarian state 3 billion euros in inheritance tax, which he evaded by declaring his private home a diplomatic residence).

It also does not have directly to do with his actions against the democratic opposition in Thailand, although that is quite possibly what riles up Green MP Frithjof Schmidt.

No, the real issue that, while there is no specific German or EU law, conducting government business from foreign soil is a violation of international law.

Grundsätzlich erlaubt das Völkerrecht einzelnen Staaten ihre Hoheitsgewalt in Fällen mit extraterritorialen Bezügen auszuüben, wenn eine authentische Verbindung („genuine link“) zwischen dem tätig werdenden Staat und dem von der jeweiligen staatlichen Handlung Regelungsgegenstand besteht; in Abwesenheit einer solchen Verbindung, darf ein Staat hoheitliche Akte in einem anderen Staat nur dann vornehmen, wenn letzterer zustimmt.

In principle, international law allows states to exercise their executive power in cases with exterritorial connections, if there is a genuine link between the acting state and the subject affected by the regulatory action of the acting state; lacking such a connection, a state may perform sovereign tasks in another state only if the latter state agrees.

The source is an expert opinion by the "Wissenschaftlicher Dienst des Bundestages", the expert service that does the scientific footwork for German MPs. The translation is mine, and believe me when I say the original version of the first half sounds just as garbled in German as it does in my translation. Please refer to the original for the list of primary sources (footnote #2. There is also a bit how judicative and legislative bodies enjoy a little more leeway that the executive, but a king is undoubtedly the executive power, so that's not relevant).

However, the closing part of the paragraph seems unambiguous, and since Germany has not given permission to the Thai king to conduct government business (and can hardly do so, since by our constitution we have to hold up democratic values), Rama X is violating international law (and since German law must not disagree with international law he is violating German law, too, even without any specific paragraph).

Answer 2

A foreign monarch in a country is probably, from a legal and technical point of view, present in that country on a diplomatic visa (whether or not the paperwork involved is actually done). Generally, a country has the right to direct anyone who is present in a country on a diplomatic visa to depart for reasons determined in that country's sole discretion.

So, just as Germany could tell any particular foreign diplomat to leave without a justiciable cause for doing so, Germany could say the same thing to a foreign king for any reason it deemed fit.

It may or may not be actually illegal until the country affirmative tells him to leave. I agree with you that it probably isn't illegal until the foreign ministry says so. But the foreign minister can summarily make it illegal to do so at any time.