craftbukkit/nms-patches/net/minecraft/world/item/ItemBlockWallable.patch

--- a/net/minecraft/world/item/ItemBlockWallable.java
+++ b/net/minecraft/world/item/ItemBlockWallable.java
@@ -10,6 +10,12 @@
 import net.minecraft.world.level.block.Block;
 import net.minecraft.world.level.block.state.IBlockData;
 import net.minecraft.world.phys.shapes.VoxelShapeCollision;
+// CraftBukkit start
+import net.minecraft.server.level.EntityPlayer;
+import org.bukkit.craftbukkit.block.CraftBlock;
+import org.bukkit.craftbukkit.block.data.CraftBlockData;
+import org.bukkit.event.block.BlockCanBuildEvent;
+// CraftBukkit end
 
 public class ItemBlockWallable extends ItemBlock {
 
@@ -49,7 +55,19 @@
             }
         }
 
-        return iblockdata1 != null && world.isUnobstructed(iblockdata1, blockposition, VoxelShapeCollision.empty()) ? iblockdata1 : null;
+        // CraftBukkit start
+        if (iblockdata1 != null) {
+            boolean defaultReturn = world.isUnobstructed(iblockdata1, blockposition, VoxelShapeCollision.empty());
+            org.bukkit.entity.Player player = (blockactioncontext.getPlayer() instanceof EntityPlayer) ? (org.bukkit.entity.Player) blockactioncontext.getPlayer().getBukkitEntity() : null;
+
+            BlockCanBuildEvent event = new BlockCanBuildEvent(CraftBlock.at(world, blockposition), player, CraftBlockData.fromData(iblockdata1), defaultReturn);
+            blockactioncontext.getLevel().getCraftServer().getPluginManager().callEvent(event);
+
+            return (event.isBuildable()) ? iblockdata1 : null;
+        } else {
+            return null;
+        }
+        // CraftBukkit end
     }
 
     @Override