Interact - Sending Back PickList Values

Use Case:

I'm creating a Interact rule that will allow our users to log any issues they encounter with Clarizen itself and assign to our Clarizen Admin group.

One of the input variables is System, which links to our custom field Request.HachetteInternalSystem, which can have one of the following values:

* Distribution

* Publishing

* Clarizen

* etc

This is fine. The issue arises when a user inputs a value for System that doesn't exist. What i currently do is use Catch and report the issue back to the user and set a default.

Question:

Is there anyway of giving back to the user all the valid values of a PickList field collection without hardcoding?