Obviously what they are doing is not illegal as they are still doing it. They are very good at gaming the system.
There exist regulations to establish a "National Market", but the reality is that right now there are 14 different exchanges*, and therefore 14 independent order books to participate in. The HFT that you object to in particular is the style that performs arbitrage among the order books. If you think that arbitrage is front-running, you should start complaining to the SEC about the massive fragmentation in the US stock market which creates this situation in the first place.
* NYSE, NYSE ARCA, NYSE MKT (formerly the American Stock Exchange), NASDAQ, NASDAQ PSX (formerly the Philadelphia Stock Exchange), NASDAQ BX (formerly the Boston Stock Exchange), NSX (formerly the Cincinnati Stock Exchange), CBOE, Chicago Stock Exchange, BATS, BATS-Y, EDGX, EDGA, and now LavaFlow. Notice that's 14 exchanges with three owned by NYSE, three owned by NASDAQ, two owned by BATS, two owned by DirectEdge. Clearly market fragmentation benefits the exchanges.