Stop orders become mkt orders when the price point is reached. Limit orders stay limit orders until you change them.
Huron, from the information you provided you just used the wrong order type. You placed a sell limit order below the current market price and were executed. Limits execute at or better than the price you entered (for a sell order 0.75 is better than 0.65 hence the execution). You needed to place either a stop market or stop limit order. Unless there is some other information not listed here, the broker simply executed the trade as instructed.
There are no laws, regulations, or "ethics"... That apply to retail orders in 2012... Retail is nothing more than cannon fodder for Wall Street. Yeah, you can technically find regulations one might think apply... But it's all just Kabuki Theatre... There are endless "exemptions"... That encourage indiscriminate pounding of your Back Orfice. That's why you have to understand how to limit your profile... And why your Profit Margins MUST be at a certain level... I would say at least > 30-40%... So you can absorb the inevitable cheating.
If you place a limit sell order at a price below the current best bid and the market is open, you're entitled to be filled at the current best bid (if there are enough shares there). Note that the bid can be 5 or 10 cents below the last trade price. If your limit sell order price is higher than the best bid, you might get filled at your price, or you might not get filled at all. The stock you traded has a pretty wide bid/ask spread outside of regular trading hours. On 5/4, prior to 8AM (which is when Ameritrade customers can start trading), the bid/ask was .631 x .84. At 8AM, one or more limit orders for .65 appeared, and got filled. I see one trade for 9900 and one for 1600.