Can an American Citizen Kill a Member of the Cartel on American Soil?

I asked if Americans should be allowed to kill fentanyl dealers and let's say cartel members on American soil. And a lot of people said, absolutely. Yeah, you could kill that person. That would be self-defense in every definition. Now in my opinion, it should be legal. You just have to make sure the dads get pushed far enough. If ever there's this situation and I predict it will happen, I don't recommend it. But the government has checked out. The government is allowing the invasion to happen.