The Interislander ferry company plans to challenge the Marlborough District Council if it pushes ahead with a new harbour safety bylaw.
Under the law, the council will introduce a new multi-million dollar navigational identification system and will charge commercial operators to recoup costs.
That would cost the Interislander about $600,000.
General manager Thomas Davis, says the law won't improve safety and the company will appeal against such a bylaw.
Mr Davis says accidents in the Marlborough Sounds relate to people in recreational vessels and the proposed bylaw doesn't address that.