A High Court challenge against the Tasmanian Government's controversial workplace anti-protest laws is set to go ahead, despite police discontinuing prosecution against the only five protesters to be charged under the laws.

Tasmania Police has decided not to prosecute any of the protesters charged under the State Government's new workplace protection laws, which aim to crack down on activists disrupting forestry and mining activities.

Five people, including former Australian Greens leader Bob Brown, were charged during a forest protest at Lapoinya in the state's north-west in January.

In May, police decided not to pursue the charge against Mr Brown because he was directed to leave a "business access area", when he was actually on a "business premises".

On Friday, police dropped charges against two other protesters for the same reason.

Police said the remaining two were not given instructions strictly in accordance with the Act when given a direction to leave, rendering their subsequent charge for returning to the area invalid.

Mr Brown said he and another protestor, Jessica Hoyt, would still push ahead with a High Court challenge to the legislation.

"It infringes the inherent right of people to peaceful political protest," Mr Brown said.

"The laws are so badly drafted and Premier [Will] Hodgman needs to rescind this piece of shoddy legislation."

Ms Hoyt said the legislation did not hold up.

"I think the fact that the charge is dropped shows that the law is wrong," she said.

Forestry Minister Peter Gutwein said it was disappointing police would not prosecute the protestors, but he had been advised the decision was based on "purely technical matters".

The Government aims to have the High Court case discontinued.

A directions hearing is expected on June 29.

In a statement, Tasmania Police Assistant Commissioner Glenn Frame said officers were being given appropriate guidance in relation to the application of these particular sections of the Act.