of international law and conduct
The principles of international law and conduct are derived from the principles of individual conduct:
Any individual who is not willing or able to control its inner drives and thereby violates the rights of another individual is considered a criminal and in some cases as mentally deranged. This is true in every state or nation on this planet.
The same rule applies to the states. Any state must control the individuals and groups within and subdue them to its law. Of course the state cannot avoid that some individuals commit criminal actions, but it can put these individuals to justice, at least it must give its best trying. Similarly the state may not be able to avoid criminal actions by groups of its citizens, but it is obliged to enforce criminal prosecution.
If a state is not willing or able to control its inner forces and if thereby the rights and borders of another state are violated or threatened to be violated, this state has to be considered a criminal state or a state in the state of civil war. In both cases international actions have to be taken against this state.
As long as there are private armed forces within a state that are not 100% subdued to the rule of law [as for example private security services in western democracies are – in contrast to groups like Hamas in Palestine or the armed forces of the drug bosses in South America], this state has to be considered as being in a state of civil war [or as supporting these groups].
In terms of individual conduct such a person would be called a schizophrenic [or a criminal]. As soon as such a person would threaten to harm anybody society would take action and lock this individual up in a psychiatric ward [or in prison] for the full duration of the implied danger.
Therefore: In case a state is not willing or able to control its inner groups and either itself or other nations are in danger to get hurt the international community is obliged to intervene and to enforce control over these groups or – if no international force would be installed to take control over such a state – other states whose rights are infringed by such uncontrollable groups would have the right to intervene to protect its citizens.