Learn English – Who do you think I (Met / met with)

A. The official from X association

The person that I am talking about is coming from that association. I probably expect that person to act, while they are here, on behalf of that organisation.

B. The official for X association

That is one of our own people, not a member of, or acting for that association. It it the person, that for us, keeps in contact and deals with that association.

C. The official with X association

More or less the same as A), but in this case it is certainly true that the person is here in their role as member or representative of the association. You might hear this phrase on a news-item, if someone is called upon as an expert: "And to answer some questions about X, here is ms. Y, who is with the X association."

D. The official at X association

The person is working for, or physically at the premises of X association, but I am not necessarily talking to or otherwise communication with them.

"...substitute for the criminal justice system..." is correct in your example. You always substitute something for something else.

I can think of a situation in which you'd use "to" after "substitute":

I used a substitute to avoid going to the grocery store.

However, in that example you're just not saying the part where you've substituted something for something else, shortening the sentence. The "to" phrase isn't telling us what was substituted; it's just telling us why something was substituted. We can include it with the other part:

I used a substitute for the buttermilk to avoid going to the grocery store.

or

I used a substitute for the buttermilk in order to avoid going to the grocery store.

The "to" has nothing to do with "substitute", which pretty much always takes "for".