You just have to disclose, that's it. Your supervisor may also say no. They don't want a conflict of interest at some firms. With the smaller futures brokers it wouldn't be a problem. They front run their own customers anyway.
How can they front run in general in non-pit markets? Dont get me wrong, but... how would you front run an electronid 1 lot buy order at the marget for the ES? Wont make any difference and as a broker you dont earn any money on it. To front run one needs IMHO a pit