Not that the Canadians would ever do it, but suppose a Canadian citizen came across the border to the US with an automatic rifle and started blasting away, killing people. The laws on the books in the state the Canadian entered would require that he be arrested and charged with murder. The Canadian government would agree that that was proper.
Now, suppose that a whole bunch of Canadians in military garb and equipped with military weapons came across the border and killed a whole bunch of people. According to the same law they would be subject to the same arrest and same charge of murder. But in this case the Canadian government would not agree to the arrest and murder charge against their soldiers because they would claim that they had declared war on the US.
Under the current conventions of war everyone would say, "Oh, well, they can't be charged with murder because they've declared war." This means that any nation can abolish the laws of another nation as it applies to them by the simple act of declaring war. This doesn't stand up to examination because it ignores the fact that the invaded country's law against murder is still on the books and is still in effect. And it's still against the law to murder people where that law is in effect, even if the murderers have declared war. No one country can abrogate at will the laws of any other country.
The Iraqi Penal Code, 1969, Third Edition, 1988, which was in effect in March, 2003 when Bush invaded Iraq, Chaptger 3, Section 1, murder and attempted murder, is an offense against Iraqi law.
George Bush violated Iraqi law by invading Iraq and killing a whole bunch of people. While it's true that he violated international law, the Geneva Convention, the United Nations Charter, common decency and common sense, none of those organization's people were killed. It's the citizens of the country who's people were killed because their laws were violated who have the absolute right, duty and obligation to uphold their law and arrest and charge the invader with murder. They and only they have the authority to enforce their law.
Maybe we know now why Bush doesn't want to remove his military force from Iraq. If the Iraqi government ever gets it's sh*t together and notices Chapter 3, Section 1 of it's Penal Code, Bush will be subject to a murder charge. In Iraq. By the people who's law was violated and whose people were killed. And that would be an act of justice for the people of Iraq.