in Judges, some people were risen up by God to bring Israel out of the hands of other nations. But why do so many of them murder other people? Ehud stabs a king and Jael drives a post through Sisera's head. I thought God wasn't allowed to lead people into murdering other people?
"Surely for your lifeblood I will demand a reckoning; from the hand of every beast I will require it, and from the hand of man. From the hand of every man's brother I will require the life of man. Whoever sheds man's blood, By man his blood shall be shed; For in the image of God He made man" (Genesis 9:6-7).
Do we count the man who delivered justice against someone who committed murders among the murderers? Isn't doing so losing track of why the problem existed in the first place? Notice that God requires man to not suffer a murder to live. What is different? A murder kills because he feels justified in taking another person's life. He might be taking revenge on another person or just enjoys killing people. The man bringing justice isn't necessarily motivated by revenge or enjoyment. A grave sin is committed and he is acting because laws were broken. It isn't about him, it is about justice being served.
"And the children of Israel again did evil in the sight of the LORD. So the LORD strengthened Eglon king of Moab against Israel, because they had done evil in the sight of the LORD. Then he gathered to himself the people of Ammon and Amalek, went and defeated Israel, and took possession of the City of Palms. So the children of Israel served Eglon king of Moab eighteen years. But when the children of Israel cried out to the LORD, the LORD raised up a deliverer for them: Ehud the son of Gera, the Benjamite, a left-handed man. By him the children of Israel sent tribute to Eglon king of Moab" (Judges 3:12-15).
We aren't told all that Eglon did to Israel during his eighteen year rule. I know it wasn't pleasant because it caused the people of Israel to cry to God for deliverance. When Ehud killed Eglon, he stated that this death was a message from God. Technically, it was the first act of war to repulse Moab from Israel because when Ehud returned: "Then he said to them, "Follow me, for the LORD has delivered your enemies the Moabites into your hand." So they went down after him, seized the fords of the Jordan leading to Moab, and did not allow anyone to cross over. And at that time they killed about ten thousand men of Moab, all stout men of valor; not a man escaped" (Judges 3:28-29).
While God allowed Moab to invade Israel as a punishment to Israel, it did not justify Moab's behavior. God took advantage of their aggressiveness to accomplish an end, but Moab was still responsible for how it behaved, which includes its king.
"So the LORD sold them into the hand of Jabin king of Canaan, who reigned in Hazor. The commander of his army was Sisera, who dwelt in Harosheth Hagoyim. And the children of Israel cried out to the LORD; for Jabin had nine hundred chariots of iron, and for twenty years he harshly oppressed the children of Israel" (Judges 4:2-3).
Again we see a conquering nation allowed to punish Israel and again we are told that the conqueror's treatment of the Israelites was harsh and oppressive. I would not at all be surprised if it included the murder of innocent people. In this case Barak led the Israelites in war against Sisera and his army. Despite having the technical advantage, Sisera lost the battle and tried to escape on foot. "And the LORD routed Sisera and all his chariots and all his army with the edge of the sword before Barak; and Sisera alighted from his chariot and fled away on foot. But Barak pursued the chariots and the army as far as Harosheth Hagoyim, and all the army of Sisera fell by the edge of the sword; not a man was left" (Judges 4:15-16). But what about the leader? Does he get away with the twenty years of evil that he did?
He ran until he reached the house of Heber, a Kenite who had a treaty with Sisera's king. Heber's wife, (an Israelite based on her Hebrew name) convinced Sisera to stop and rest. She then killed him while he slept. There was a reason God made use of a woman to strike down the leader of the oppression. Barak refused to go to war as God commanded unless the prophetess Deborah went with him. "Then she sent and called for Barak the son of Abinoam from Kedesh in Naphtali, and said to him, "Has not the LORD God of Israel commanded, 'Go and deploy troops at Mount Tabor; take with you ten thousand men of the sons of Naphtali and of the sons of Zebulun; and against you I will deploy Sisera, the commander of Jabin's army, with his chariots and his multitude at the River Kishon; and I will deliver him into your hand'?" And Barak said to her, "If you will go with me, then I will go; but if you will not go with me, I will not go!" So she said, "I will surely go with you; nevertheless there will be no glory for you in the journey you are taking, for the LORD will sell Sisera into the hand of a woman." Then Deborah arose and went with Barak to Kedesh" (Judges 4:6-9). Because Barak hesitated, the key victory was not his but given to another.
This was just the beginning of the war for independence and Jabin eventually lost. What happened here was that God put Sisera and his men under an death sentence for the evil they had done. Barak and his men were carrying out God's justice, and so Jael, Heber's wife, was given key part in that punishment.
Regarding the right of countries to defend its citizens, see: Vengeance.
I do have one more question concerning this though. The reason that people were allowed to kill these rulers was for the sake of justice, right? And that makes sense, but I thought that judgement wasn't supposed to be reserved for man to decide, but for God to decide? But since God directly led these people, then it was God deciding in the end anyway, right? But since God doesn't directly speak to people anymore (as in there are no more prophets), then does that mean that killing rulers for the sake of justice is as of today a sin, whereas back in those days it wasn't? Or is clear cut injustice still a valid reasoning for killing someone?
God can and has delegated limited authority to some people. For example, judges were considered representatives of God. They were required to take God's laws (they weren't allowed to make up their own laws) and apply them to situations. The decision for when a law applied was then man's, but the laws themselves were God's.
This put extra burdens on the judges because God, the ultimate Judge, will hold them accountable for their decisions. See "Just Justices" for more about this.
God also delegated to government the responsibility of protecting the innocent.
"Let every soul be subject to the governing authorities. For there is no authority except from God, and the authorities that exist are appointed by God. Therefore whoever resists the authority resists the ordinance of God, and those who resist will bring judgment on themselves. For rulers are not a terror to good works, but to evil. Do you want to be unafraid of the authority? Do what is good, and you will have praise from the same. For he is God's minister to you for good. But if you do evil, be afraid; for he does not bear the sword in vain; for he is God's minister, an avenger to execute wrath on him who practices evil. Therefore you must be subject, not only because of wrath but also for conscience' sake. For because of this you also pay taxes, for they are God's ministers attending continually to this very thing" (Romans 13:1-6).
Again, because God delegated the authority to them, those in government will be accountable to God for how well they carried out their assigned task. There have been rulers of countries who have been removed because of the crimes they have committed. Given human nature, I'm sure there will continue to be such cases in the future as well.
Thank you for your help.