What would constitute "proof"? By these standards US submarines in WW2 could not target merchant ships because the crews were 'civilians' with no proof that they belonged to the NAZI party. It's insane. Besides. You blast a few trucks and either one of 2 things happens: The driver say "scr3w this" and stop hauling, or they continue, in which case you can safely conclude that they are jihadists.
Obama’s ROE.