Lean manufacturing believes in fool proofing the processes so that the process itself will avoid the problems. This is known as pokayoka. This is actually a system where the problem will be detected as and when they occur and then corrective action will be taken avoid the problem. More importantly here, measures are taken to avoid the possibilities of that problem coming up. Controls for me are end of pipe system of fighting problems. For an example if a procurement manager requires to sign and authorize purchase orders which are above a certain value, if this control to be really effective the manager must go through the history of this PO and validate every step of this process and then do the authorization. If he finds a problem he will ask for explanations from his subordinates and ask them to correct it. Otherwise he will authorize the PO with his signature. But in reality how many of the managers go into that depth before they authorize it. It becomes a routine task to sign the purchase orders coming to him. So that control adds a non value adding activity to the system and also complicates the processes. On the other hand if the purchaser wants he will create two purchase orders with half the value of the original each so that the limit will not be exceeded. So for me controls like this becomes only processes which are none value adding and also time consuming. If any organization wants to have this kind of control in purchasing I believe it is simple to ask the manager himself to raise the PO which is above a certain value. This will save his time and will serve the purpose since it has a focus responsibility.
But still I do not like the concept of controls. I believe trusting people to do their job is an easy way of doing this. People do not like to do wrong things unless they feel they should. One way of making them to feel to break the rules and trust is to impose many controls on them. When there is a control on them, there is always a workaround.
To effectively have a control, build the disciplines to the system itself. In a lean environment above requirement might not be their since the ordering is taking place when the requirement is there to the required quantity. So no problem for over ordering here. If someone has over ordered then it will get highlighted immediately and corrective action can be taken.