From the official SO websiteOkay, thanks guys.
But mechanism aside, the rules say the traps have to be unmodified. I cut off part of the snapper on my traps and put in a bar to extend the lever arm to get more leverage when operating the trap. Is that considered modifying the trap? If so, how else would you add on and extend a lever arm from the spring? O_O
"An unmodified mousetrap is one that still retains its original structural integrity to function as intended. Altering the structural integrity of the mousetrap includes, but is not limited to, welding, bending, and cutting of the restraining bar."
You're going to have to ask yourself if the structural integrity of the device was compromised when you did your modification along with whether or not the mousetrap can still function as intended (ie kill a mouse). If you can't fulfill all the above conditions, then the mousetrap would be considered modified.