That's bizarre. So let's say AAPL is trading at $120, and you put in a limit order to buy it at $110, then you should never be allowed to cancel it? How long does the order sit there for? What if AAPL's price goes up to $400 over the next few months, do you have to leave your limit order there forever?
I don't think fenollop means not withdraw it at all. He means after someone has said "I'll take that offer". At which point you can't withdraw it. So these people will make a loss of enough people take up their offers. This risk is mentioned in the article. It doesn't explain why "spoofing" is illegal though. It should be legal. They are trying to shift the market (so is everyone) through an action that exposes themselves to massive loses.
You are not allowed to do this if you are a simple guy from the street.