What are some political philosophies/doctrines for deciding when violence is acceptable?

Question

Recently some UK politicians have been getting milkshakes thrown over them. No injuries resulted, but the question of when violence, including relatively minor acts such as this, can be justified or viewed as acceptable came up again.

What are some political philosophies that include violence as an eventual resort, under some specific circumstances? For example, the US 2nd Amendment seems to suggest that violence against government employees may be justified sometimes, i.e. the "well regulated militia" clause is interpreted by some as the population retaining the option to violently overthrow the government.

Another example would be various anti-fascist groups and white supremacists, but I'm asking about political philosophies so things like conspiracy theories (e.g. the "race war" or "great replacement") are not really on-topic.

Answer 1

In Germany, there is the concept of Widerstandsrecht (right to resistance, or right to revolution) (both wiki articles go into more detail as well). This right is part of the German constitution:

Gegen jeden, der es unternimmt, diese [verfassungsmäßige] Ordnung zu beseitigen, haben alle Deutschen das Recht zum Widerstand, wenn andere Abhilfe nicht möglich ist.

_{All Germans have the right to resistance against anyone trying to remove the constitutional order if no other remedy exists.}

This is meant as protection against a state that behaves unconstitutional, as well as individual people or groups which threaten the democratic nature of the state (fascists trying to change the democratic nature of the state for example, to get back to your example of throwing milkshakes at Tommy Robinson, etc).

It's mostly a theoretical right, because when a democratic state is working, there are likely other remedies. If it's not working, the article can't be enforced legally.

Answer 2

When injustice becomes the law, resistance becomes a duty.
ascribed to Bertold Brecht, but apparently paraphrasing Leo XIII

Within a state, resistance becomes acceptable if the legal system shows a grave, systematic disregard for principles of human and civil rights and recourse to the courts is no longer possible because the courts accept this injustice. (Violence would also have to meet tests of proportionality and effectiveness.)

This is not the case in the UK right now, so the violence is not justified on Leo's guideline.

Answer 3

All of them

Every political ideology is a way of deciding the legitimate application of power - who should control it, and who it can be used against. This universally legitimises violence somewhere in the system, since the application of power over others is violence.

In most nations, it has been agreed that the state should have a monopoly on legitimate violence. They therefore control the primary means of violence domestically (through a police force) and internationally (through the military). The laws of the nation and the judicial system set out who the state may act violently toward.

Even Pacifism, an ideology which exists to oppose violence, legitimises either violence performed in self defence, or allows any violence that cannot be stopped without those trying to stop it resorting to violence.

It should be noted that this does not mean that every ideology is essentially the same - only that politics is all about violence, so to ask for examples of ideologies that deal with violence is flawed as a question, since every political movement uses, legitimises or allows violence in some way.