Oh my goodness, what an idea! Why didn't I think of that?

Only if you’re not the government.

I mean that's basically what the war is about: who all is the government where (i.e. who can arbitrarily kill people legally).
The exclusive right to commit violence is a standard feature of governments, yes.

If someone tries to kill you just say "no thank you."

Legally they cannot kill you.

If you do not consent, their bullets cannot enter your body either

Permanently Deleted

It's only legal to kill people when rich people can profit from it

Calls to mind the end of Month Python and the Holy Grail wherein the massed armies of King Arthur are rounded up and arrested by some constables for disturbing the peace upon the moors.

That ending was such a cop-out

TikTok girl ends all war

Although one wonders if "War and Peace" would have been as highly acclaimed as it was if it was published under its original name "War: What Is It Good For?"

VHAT IS ZAT BEEPINK?!?
- Fun fact: that same actor also played Admiral Hanson in the classic Star Trek: The Next Generation 2-parter "The Best of Both Worlds."
Come on Jerry, that's not real!

Legit question ngl

But they have a point, how can people legally kill other people, will every case be checked?

not literally every case, but yes there are international laws (e.g Geneva Conventions, Hague Conventions, Convention on Certain Conventional Weapons) in place detailing who is allowed to kill who and in what way.
By disabling the rule of law in an area. The legal government and law enforcement is overpowered and you get a zone of martial law by the strongest force present, which may or may not be bound by a mandate of their origin country, and hence could be held responsible and controlled for acts outside of their mandate.
Isn't the point of official "declaration of war" thing is to kill people legally?
- what if it's not really a war, not that formal just a casual occasion like it's just a holiday that somehow became a special military operation