US federal law regarding threats to kill.

political analyst

This article is from 2021.

https://edition.cnn.com/2021/01/26/politics/marjorie-taylor-greene-democrats-violence/index.html

Even though the 1st Amendment of the US Constitution protects freedom of speech, it doesn't permit the threatening of someone's life. I believe that it is a crime to threaten to kill a serving US president.

Were there no grounds to put Marjorie Taylor Greene under investigation on suspicion of making threats to kill former president Barack Obama and other prominent Democrats and federal officers? If there were grounds, why was there no investigation?

Peregrinus

In general, "threatening" offences involve making threats to the intended victim. If I threaten you with harm, that may an offence, but if I say to Donald Trump that I would like to harm you, or if I say to you that I would like to harm Donald Trump, that's less likely to be an offence.

Or, I should say, it's less likely to be the offence of threatening someone with harm. It way well, depending on the facts and circumstances, be a different offence - incitement, say, or conspiracy.

The article you link to is light on detail, but much of what is alleged against Boebert is not that she posted threatening to harm people, but that she "liked" such posts by others. Simply liking the posts of others is probably not enough to amount to any kind threatening harm, incitement or conspiracy offence. That's not to say that there might not be some posts of Greene herself that could amount to an offence. I don't know whether anyone is investigating this. But, from memory, Greene has been the subject of attempt to expel her from Congress for her threats of violence against Members o Congress.