Tiered Depths

This is a crafttweaker addon that allows the packmaker to restrict mining levels based on the y level.

Syntax: 

mods.td.TieredDepths.addBlacklist(IBlockStateMatcher blackListedBlock, int maxHeight, int dimension, int minimumMiningLevel);

Example:

mods.td.TieredDepths.addBlacklist(<blockstate:minecraft:stone>,32,0,1);

 This line prevents stone from being mined at y=32 or lower using a wooden pickaxe/equivalent in the overworld.