The problem of course is that those ornaments aren't REALLY toys. They're decorations. So, the rule is "Look, but don't touch." He has a really hard time with that.
Mom finally gave him an ultimatum after about the millionth approach to the tree with ITT ("intent to touch," for all you who haven't watched the latest Night at the Museum). "Touch it one more time, my darling, precious child," she said through clenched teeth, "and I'll send you to bed." So he sat there for about a minute, with his arms tightly crossed, looking sideways at the tree which was within his reach, but out of his grasp. Then, when he thought we weren't looking--- ITT!!, and he TOUCHED! When I got out of my chair, the look on his face was a combination of terror, consternation, and a strange satisfaction at having touched.
As calmly as I could (which, happily, was pretty calm this time), I frog-marched him off to his toddler bed and firmly laid him out with his blankie. "Stay put," I warned, and left the room. Within a minute the wailing started....
It's been going for 20 minutes (sigh). Ah, the joys of parenthood.