[tptacek]

If that's true, you should be able to cite a statute, an SEC/FINRA/CFTC rule, a court ruling, or an exchange rule to explain how (allowed and prohibited behavior on markets being defined by all four of those kinds of sources, frustratingly enough).

I suspect you won't be able to find any such source. Malfeasance by trading firms makes career cases for prosecutors.

That's not to say, normatively, that that's how things should be: obviously, prosecutors are not making much of a dent in the trustworthiness of big financial firms.