Carter Holt Harvey has been fined $10,000 over an unlawful drug test.

The company must pay the money to the Engineering, Printing and Manufacturing Union after it used the pretext of a random drug and alcohol test to deny site access to a local union organiser.

Corey Wallace was banned from the Carter Holt Harvey site in Nelson after he refused to take the so-called random drug test.

The EPMU's Alan Clarence says they're pleased with the Employment Relations Authority ruling which has found the actions were unlawful and in breach of its good faith obligations.