Is the expression "it is going to not help" correct? and is this general expression?
This is not a generally accepted way of speaking. Some opposed the use of this thing called “split infinitive” as in: "I want to not forget her." The "not" coming between the two parts that make up the infinitive is sometimes viewed unacceptable. Moreover, the “to” is actually an infinitive particle; it cannot be subsumed under any part of speech, so it’s vital that you keep it closest to the verb. You don’t want to interrupt the linguistic continuity of a phrase traditionally viewed as one word. So, I highly recommend you use this sentence like "It is not going to help law enforcement." not splitting the infinitive.