[usefulcat]

I can imagine ways that order spoofing would look significantly different from legitimate (if possibly high frequency) trading activity. For example, if I'm constantly sending and cancelling a single order, that might look a bit like spoofing. Or it could be a glitch in a trading algorithm, or possibly even a legitimate reaction to some other periodic, high frequency pattern in the market data.

OTOH, if I send 100 orders and then immediately cancel all of them, and especially if I do that repeatedly, I can't think of a legitimate reason for that; why not just use a single order? This matters because when those orders show up in the market data, I'll know that all (or most anyway) of them came from me, but other market participants will not know that those orders all came from the same participant.

This kind of behavior would not be difficult to look for in the market data, especially after the fact, so I don't buy the argument that laws which forbid such behavior are 'unworkable'.

Source: have been doing algorithmic trading for many years