Anonymous question

The question itself already contains part of the answer. Since we are talking specifically about a Libertarian Russia, this already implies a minarchist scenario. Within this scenario, diplomacy, the protection of citizens from external aggression, and the enforcement of court decisions remain in the hands of the state.

Why diplomacy is the easiest to explain. If there are states in the world, it means there can be interstate agreements, and therefore it is necessary to maintain a certain state structure that will prepare and sign these agreements.

In a similar way, one can understand why the protection of citizens from external aggression becomes a matter for the state. It is easy and pleasant when external aggression is carried out by some bandits who are not part of the privileged club of state bandits. A private company can handle them without any diplomatic consequences. However, it would be difficult for a private company to explain to someone like Kim Jong Un that he is wrong: to him, they would look like some terrorists with whom negotiations cannot be conducted, if only because there is no one to talk to: the state considers only another state as a counterpart.

The most questionable justification is why the state should be allowed into the sphere of enforcing court decisions. But even here, one can refer to possible incidents with foreign companies, who might perceive violence against them by private actors as lawlessness and run to complain to their own government.

In any case, this is how minarchists envision the desired future, and I, generally, am not against it — but only until non-state practices begin to be actively implemented in these three areas as well.