http://www.usatoday.com/news/washington/judicial/2010-06-21-supreme-court-anti-terror_N.htm Interestingly, this case was argued by the Solicitor General, Elena Kagan, who argued: http://www.usatoday.com/news/washington/judicial/2010-02-23-terrorism-law-appeal_N.htm?csp=obinsite The logic should be obvious, but since she doesn't finish the thought, I'll do it for her: if you provide concrete to build homes to Hezbollah, you allow them to build the same number of homes for less money, freeing up resources for them to use to build bombs. Hamas is also on the list of such terrorist organizations. What this means for blockade runners is clear: even if you're just providing concrete to civilians in Gaza, you're supporting terrorism and violating US law. And this is a line of logic that if I hadn't explicitly supported in the past (don't remember), I certainly considered and agree with. Now, the question is - if American citizens are found among blockade-runners, will they be arrested and prosecuted? That part may be a question of jurisdiction.