I have a question that I am a bit ignorant about. The teens (as well as a few other stories I've heard on the news) that were leaving the country to join ISIS were arrested by FBI IIRC. I believe this was the case with a few other people. My question is were there other things these people have done to warrant being arrested? My thought process was they were arrested just for wanting to go do "something". Did I miss something in any of these stories? If I say that I want to go steal/do xyz, can I be arrested just for saying that I'd like to do something. I know that people making threats to the POTUS get strung up but what am I missing here those of you more educated in law than I?