Highland police have referred a complaint about the legality of tolls on the Skye Bridge to the procurator fiscal.
Tolls have been challenged since the bridge opened
It is the first time Northern Constabulary has acted on such a matter and protesters said the move was significant.
Northern Constabulary took two weeks to read campaigner Robbie the Pict's 39,000 word statement claiming that the tolling regime on the Skye Bridge was illegal.
The force, which has been accused of dismissing such complaints, has now passed the matter to the fiscal.
The Skye Bridge Company, which collects the tolls, declined to comment on the move.
But the Scottish Executive said all challenges to the legality of the toll regime had been rejected to date and ministers did not expect that to change.
Campaigners have previously taken their case through the Scottish courts, but lost their challenge in 1999.
Four protesters argued that the toll collectors' employers, Miller Civil Engineering, had no lawful authority to collect the money for crossing without the written consent of the secretary of state.
But three judges hearing their appeal in Edinburgh called their action "misconceived".
Robbie the Pict was among the four campaigners who had been convicted of not paying the tolls.
Tolls for crossing the bridge are currently set at £5.70 one-way for a car in the summer and £4.70 in the winter.