Sovereign states do whatever they want. Most countries (if not all) have a legal framework for expelling foreign citizens on grounds of national security or for

Sovereign states do whatever they want. Most countries (if not all) have a legal framework for expelling foreign citizens on grounds of national security or foreign policy (and it's up to them to decide what constitutes that). This is accepted as a perfectly valid thing to do and this is what has happened here. In this particular case, it is bad manners for a state to send its agents to another sovereign state in any capacity without getting some sort of a permission from the latter.