It's commonly accepted that once you acquire soul splitter mode, everything you can do with interdiction there is a way to do with soul splitter.
Not so! I'm pretty sure I found the one area of the game where this isn't the case.
This is on the bottom level of Phariseer's tomb...the passageway that eventually leads to the area with the soul arbiter's scroll. At the beginning of this passageway, just after you walk through the door leading from the elevator, there is a gate with a pressure switch on the other side.
With interdiction, you can simply tell one of the ghosts to phase through the gate and stand on the switch. Without interdiction however, you're basically screwed here. There is no possible way to hit this switch and therefore progress down this passageway with soul splitter.
This means that, if you didn't hit this switch beforehand, once you lose interdiction there is no way to get the Soul Arbiter's scroll!!
Luckily for me, I had done this before leaving the tomb, so I was fine. But this is a warning to anyone out there who might get boned by this! Make sure you open this gate with interdiction as soon as you get it!