Welp, when you opened your account, you prolly signed an arbitration agreement, and you didn't know it. I never worked in New Accounts, but there is a reason why you signed 32 pages. Just sign here, sign there, initial here, sign there, initial here.
But there is nothing illegal for your financial institution trading against your orders. I never traded that way. I gave fair executions. And everyday, there was always one lucky retail client where I was able to break the spread and clip a trade and I gave it to the client. Oh I got MMs calling me, don't break the spread!!!!!
Just think 1/2 on 2000 shares of United Health Care @ $50.00 per share, I split the 1/4 with the client. It is only $250 to the client but it still makes retail clients happy. It retains clients. And I never knew who the retail was.