How to not allow any discounts to work on Special Price Products.

We do not want to allow any discount codes to be used on products that are utilizing a Special Price.

Use Case:
We have clearance products that are deeply discounted, but also want to provide general Black Friday discount coupons for regularly priced products. But we don't want a customer to be able to also apply Tha discount code to the special price products, as they are already deeply discounted.

Which code would we have to modify and how?

TIA,
Chad

If you can't find an existing Discount Requirement Rule plugin, you could code your own.

I'd create a new category for the "regularly priced products" that you want to discount and then create a discount with type = "Assigned to categories" and choose the new category as the "applied to category".  That way, you can specifically control which products get the black Friday discount.