Is This Chess Position Illegal? #4

Mar 5, 2011, 9:23 AM |

So you guys have figured out every one of my puzzles so far! It's impressive, so I might need to step up my game! But for now, lets keep it cool and fresh with a natural puzzle. Should be easy to find the missing legal move, even for beginners. However, I won't make puzzles like this much longer! My future puzzles will begin to evolve into much much harder forms! Let's see who finishes this puzzle first!

"I find it quite fun to search a chess board to see if a certain position is legal or not. And by legal, I mean it is a something you can find in a normal game. Is this position able to happen in an actual game? In other words, is this position legal or illegal? Post your answer, and tell me what you think the answer is. Any and all chess variations accepted. If illegal, also tell me what is wrong with the position. I'll post the solution when someone answers correctly."