Here’s an excerpt of relevant law:
8 U.S. Code § 2384 - Seditious conspiracy
If two or more persons in any State or Territory, or in any place subject to the jurisdiction of the United States, conspire to overthrow, put down, or to destroy by force the Government of the United States, or to levy war against them, or to oppose by force the authority thereof, or by force to prevent, hinder, or delay the execution of any law of the United States, or by force to seize, take, or possess any property of the United States contrary to the authority thereof, they shall each be fined under this title or imprisoned not more than twenty years, or both. https://www.law.cornell.edu/uscode/text/18/2384
IANAL, but I think the First (and Second) Amendment ends and sedition laws begin when you actually start the actual planning and implementation.
But it’s still a big grey area IMHO. Technically Clive Bundy’s occupation of Malheur National Wildlife Refuge sounds pretty close to the letter of the sedition law to me. Then again, you don’t want to arrest people for treason every time they have a “sit in” at a Federal building or facility.
It is highly likely that a court would apply the current definition of conspiracy, deeming such an act to be a specific form within the broad definition of conspiracy.
Under most U.S. laws, for a person to be convicted of conspiracy, not only must he or she agree to commit a crime, but at least one of the conspirators must commit an overt act (the actus reus) in furtherance of the crime*. – Wikipedia
I think a key element is that your supposed goal is overthrowing the American government. That’s a pretty daunting project. Even if you convince a couple thousand people to join your movement and you have access to weapons let’s face facts; you’re going to lose the battle. You’re going to be outnumbered 18-1 just by the Coast Guard.
And that’s an important issue. In order to legally suppress speech you have to show there is a clear and present danger. That’s relatively easy when you’re trying to show that speech is advocating something like rioting or assassination. But proving somebody’s attempt at overthrowing the government was likely to succeed if unchecked is almost impossible for the reasons I gave.
They never purported to provide all the evidence justifying the strike. And, quite recently, it was revealed that they actually had some significant evidence beyond advocacy.
That said, obviously, the fact that a government flouts the rules doesn’t mean the rules don’t exist. Awlaki’s family never got a hearing on the merits about whether the strike violated his constitutional rights.