So the title says it all basically. Players can't mine blocks that require a special tool, at all. The block would just not be affected. For instance if a player tried to mine obsidian with an iron pickaxe, no matter how long they mined for the obsidian would never break. Same would apply for every other block. I don't do a lot of coding in Java let alone Bukkit plugins, but I'd assume the plugin would do something like, get the player's current held item and the block being mined, and if the tool isn't good enough to mine that block it cancels the block break event. SIMPLE, right?
