first of you have know that there is NO way to prevent a cloning of the node! the best you can do is to catch the fact that any specified node was cloned.
You can use postNodesCloned general callback which is coming with pairs of source and target nodes after they were cloned. Using this callback you can collect all unwanted "clones", and for example give a warning after that with an option to delete these "clones".
But a simple deleting of some "clones" might be not safe, in case where the cloning was happen as a part of "hierarchy cloning" process.
Using SDK you can make you own class Object which will prevent cloning. But as I said it's possible by using SDK only.
