Humanity should create a law to impose capital punishment for a politician who starts an illegitimate war, even if the legislative process would be imperfect.

Summary: The longer we wait, the longer humanity suffers from the lack of global law to punish a crime by a national leader. We should create a world law to prevent illegitimate war even though the legislative process might be far from ideal.

[Humanity needs global law now]
Humanity does not have a global law. The world can not correct the behavior of a country causing damage to other countries. When a country invades another country, there is no law and law-enforcement organization to punish the invading country, so the politician who orders the invasion can get away from that crime. That is why humanity can not stop the Russian invasion of Ukraine.

Invasion of other countries does not happen often, but when it does it poses a great cost to humanity. As we delay creating the world government and legal system, we are increasing the length of time to live under a lawless global society. It means more possibility of another invasion or even the use of a nuclear weapon. Our inability to correct global wrongdoing means a higher probability of another Ukraine or Hiroshima in the future.

[World law without voting]
Making a global law is crucial, but humanity is yet to have a global government. So we should make a law without following the traditional procedure of democracy. To begging with, we have to understand that the current legislative process is not perfect. The rule of voting is imperfect because it gives absolute power to a majority. Can a majority decide or deny anything they want? What if a majority votes to enslave a minority? Giving a majority deciding power is a convenient way to make a decision among the vast number of citizens, but it is not the perfect tool for democracy.

Voting has another limitation. In any democratic country, voting right is limited to a certain group of people. Historically it was limited only to the rich and male population. Even now, the voting right is restricted to the adult population, so a minor can not vote, let alone unborn future generations. This causes a problem in a political issue that impact multiple generations. Many governments issue bonds to serve the need of existing citizens, but the debts have to be repaid by future generations. Similarly, it would be the future generation who suffers from the environmental damage caused by the current generation. The future generations are forced to bear the costs caused by the voting of the existing citizens.

[World law supported by citizens]
So, we should make world law as soon as possible without limiting ourselves to the rule of voting. Instead of creating a law with a due process of voting in a formal government, we can write it down first and then gather support from global citizens. As the law gets more support, it becomes more legitimate and binding. The legitimacy of the law will not be binary as passing or not passing legislative process, but be more like a spectrum. The important thing is to write down a law as soon as possible without relying on conventional voting.

It is not difficult to imagine how this law become an accepted rule of the world. Humanity does not have its constitution or written rules, but democracy and human rights for example are accepted principles of the world because many people believe in them. Environmental protection used to be less accepted, but it became a common principle in the world as the number of supporters increased.

[The world law]
So, here is the first global law that humanity needs:
1) A politician who orders the military to start an illegitimate war, externally or internally, should receive capital punishment.
2) A politician who orders to use a nuclear weapon should receive capital punishment.

[FAQ]
This law is unconventional, so many people would come up with questions. So FAQ is prepared to answer some of the questions.

How legitimate is this law?
It is not fully legitimate now, but as it gathers more support from humanity it will be a legitimate world law. Also, despite its lack of full legitimacy, this is a good law that brings the benefit of discouraging a politician from wrongdoing. Instead of waiting for a perfectly legitimate law, humanity should start with an imperfect law that brings an immediate effect.

How to enforce these laws?
Now humanity does not have any formal means to enforce the law. So, we depend on individuals, teams of individuals, or organizations who volunteer to carry out the execution. For example, courageous persons in Russia can perform capital punishment by the method of their choice. Maybe there are not many individuals who would do that. However, more people, especially political adversaries, would want to do that if Putin's popularity declines. Giving a political opponent justification to kill a dictator is the deterrence not to start an illegitimate war, and this is one of the desirable outcomes of this law.

What will happen next?
If this law gains enough support from the world population, it will be legitimate and binding. If not, it will not be legitimate and even forgotten. Global citizens should spread this law so that this will gain more support.