there isn't much information around the internet distinguishing between legal and illegal front running. front running is illegal, but when? surely if we buy just before the SPY hits its 200 day moving average , where a lot of big money may enter, that is illegal? i have emailed the SEC on friday but havent got a reply, brokers i've asked won't talk as they don;t want to be held responsible. they say front running, jumping in before big orders is illegal , always, then surely placing a limit order in front of a visible block trade on level 2 is illegal? if i have a formula which large traders enter stocks in with, and front run that, is that illegal? is it illegal to wait until after the block trade has happened, then trade with it, even though it has a tendency to reverse market psychology/direction?