The 79-year-old former Greens leader was facing one count of trespass after being arrested in Tasmania's Styx Valley in February.
But the charge, as well a trespass charge against activist Colette Harmsen over the same protest, was discontinued in Hobart Magistrates Court on Wednesday.
Dr Brown said he was told state-owned forestry company Sustainable Timber Tasmania had not lawfully asked people to leave the land and hadn't properly put up signs about its operations in the area.
"(The company) brought in the police at public expense, but the whole effort was wasted because of its own incompetence," he said outside court.
Bob Brown said he was concerned giant trees had been felled in the Styx area outside a logging zone. (Matt Newton/AAP PHOTOS)
Tasmania Police said the decision to not proceed was based on "identified legal deficiencies".
"Following review of the police file and the available admissible evidence, the Tasmania Police prosecutor determined there was not a reasonable prospect of conviction," a police spokeswoman said.
"(The prosecutor) tendered no evidence in respect to this particular matter."
Dr Brown, whose foundation has dozens of people facing protest-related charges in the Hobart Magistrates Court, said it was likely others had been inappropriately charged.
Ali Alishah, who was jailed earlier in 2024 over the Styx protest, would have also had his trespass charge dropped if he hadn't pleaded guilty, Dr Brown said.
"There are other prosecutions proceeding which are not necessarily impacted by this outcome," the police spokeswoman said.
"However, each of the remaining cases will be reviewed to determine whether prosecution should continue on a case-by-case basis."
Dr Brown said he was concerned Sustainable Timber Tasmania had cut down giant trees in the Styx area outside their logging boundary.
A Sustainable Timber Tasmania spokeswoman said the company did not want to comment on Dr Brown's case.
Dr Brown was in August fined $500 for a different anti-forestry protest near Tasmania's Lake Leake aimed at safeguarding habitat of the critically endangered swift parrot.
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