Bukkit

What steps will reproduce the problem?
1.If an archer per example buy a diamond chest plate with a plugin like showcase.
2. He get the diamond chestplate and he can equiped it.
3.

What is the expected output? What do you see instead?
It should be blocked even if the player can't have it without external plugin.

What version of the product are you using?
The last : 1.0

Do you have an error log of what happened?
No

Please provide any additional information below.