I agree with Ginny, but since it is related, just a different state, and the answer is a slam dunk, and I'm bored, I'll answer re: Indiana.
Employee must authorize (hence, cannot be made mandatory); however, the DOL has stated that it will has no authority to take action against the employer if an individual is terminated for not enrolling, because IN is an "at-will employment state), so take that to mean what you will)
No provision in the law regarding employees incurring fees with the receiving financial insitution
Employee must be able to choose the financial insitution.
That's about it.