[strictnein]

It's not speech. You have a gun that fires when you say a word. You having a setup that fires the gun when you say a word instead of pulling a trigger doesn't mean you are utilizing "speech" in any meaningful sense of the word, other than that the gun responds to a sound.

[immibis]

There is no gun involved. I say the words, and the person dies. Should the government restrict my speech?

[strictnein]

Again, we don't live in a fairyland, we live in reality. A gun is real, your magic is not. If you had a gun that fired based on a sound, the fact that a sound is used does not matter. It is not "speech". Noise is not protected speech.

Likewise, if you had the magical ability to kill a random person with your magical sounds, you are not practicing "speech", you are using a magical technique in your make believe land to kill random people.