Using leaves for mulch
What specific leaves should NOT be used on the garden?
I have other do Not use plant leaves: buckthorn, pokeweed and eucalyptus. I'm sorry I omitted these in my original answer.
The key is to allow the leaves to dry and then shred them or run the mower over them to keep leaves from matting down. This creates a barrier to water and air. All tree leaves can be used. Black walnut toxin, juglone, breaks down within 2 weeks after shredding. Any effect would be minor compared to the juglone in roots. Oleander and other toxic leaves like poison ivy should not be used unless they are fully composted first.