A MAGISTRATE has questioned whether charges brought against a group of anti-CSG protesters were politically motivated and accused the police of being vexatious in pursuing them.

Magistrate David Heilpern has dismissed charges against Alan Roberts and Bradley Rankin and written a scathing judgment, accusing the police of "an abuse of the processes of the court".

The case was in relation to a protest against Metgasco drilling at Glenugie in January. Up to 30 people were charged with obstructing a driver.

To save time, a deal was done between the prosecution, defence and the court to make the case against Roberts and Rankin a test case.

But according to Alan Roberts, police withdrew the charges of "unreasonably obstruct a vehicle" just hours before the six-month limitation expired, without informing the defendants or the court.

Why else would police risk cost orders against them, drive a prosecutor up from Sydney to run the matters, arrange police witnesses to travel from Sydney, all for an innocuous minor traffic matter. It is in that context that the realistic suspicion of political interference arises

"Presumably because there were no vehicles anywhere close (by) to obstruct," he said.

A new charge "attempt to obstruct a vehicle" was laid instead.

Mr Heilpern said it was the first time he had seen a charge of "attempting to commit a traffic offence" and likened it to attempting to not wear a seat belt.

"In this case I find myself asking what could possibly be the reason for continuing on with such an innocuous charge in these circumstances," he said.

"Why else would police risk cost orders against them, drive a prosecutor up from Sydney to run the matters, arrange police witnesses to travel from Sydney, all for an innocuous minor traffic matter.

"It is in that context that the realistic suspicion of political interference arises."

Mr Heilpern said he was not convinced there had been political interference, but did find the police case was vexatious.

SCU law lecturer and CSG Free Northern Rivers spokesperson Aidan Ricketts wants to know where the order to pursue the case came from.

"There are serious questions for the State Government to answer here," he said.

"Not only has the riot squad been used to impose this industry by force upon the Northern Rivers, there is now evidence of undue process in the way that prosecutions are being handled.

"Somewhere in Sydney the orders were given for these fresh charges to be laid and we need to know how high up the chain of command these orders originated."