Canada's new moves to control and regulate shipping through the Northwest Passage and the rest of its Arctic waters may violate international rules, says the world's largest group of shipping companies.

The Baltic and International Maritime Council, whose members control two-thirds of global shipping tonnage, has objected in a formal letter to the federal government over rules that force commercial ships to register with the Canadian Coast Guard if they sail into the passage.

The council also decries Canada's decision to apply Arctic environmental legislation to waters up to 370 kilometres from the coast.

"This could be seen as effectively interfering with the right to innocent passage," reads the council's letter, sent March 19 to a Transport Canada official.

As of July 1, Canada requires all commercial-sized ships entering the Northwest Passage to report to NORDREG, a registration system maintained by the coast guard. Canada also announced it would double the extent of the jurisdiction of the Arctic Waters Pollution Prevention Act.

Both moves have been widely applauded within Canada as ways to reinforce sovereignty over waters that are becoming more navigable as sea ice melts. The steps were initially promised by Prime Minister Stephen Harper in 2008.

But few countries recognize Canada's claims to the passage. The United States, seeking to maintain the mobility of its navy, has expressed concerns about Canadian attempts to monitor and control a strategic pathway between east and west.

In their letter, the shippers make similar arguments.

They say requiring ships to obtain clearance under NORDREG suggests that some could be denied.

"Without clearance, a vessel would not be authorized to proceed," says the letter.

It argues that UN maritime rules stipulate that a reporting system be cleared through the International Maritime Organization, something Canada has not done. It also says that vessel traffic can only be monitored and controlled within national territorial waters, which extend only 22 kilometres from the coast.

Canada's extension of the waters it seeks to control "appears drastic," the letter says.

Finally, it complains that business interests weren't consulted as Canada considered the changes.

"The consultation undertaken on the proposed regulation appears to have focused exclusively on national entities," the letter says.

Officials from the council declined to be interviewed on the record on the substance of its concerns.

Reaction from the Canadian government wasn't immediately available.

Michael Byers, a University of British Columbia international law professor, said the council's letter may indicate Canada didn't do enough diplomatic work before bringing in the regulations.

While there will be little commercial shipping through the passage for the foreseeable future -- a recent survey of the shipping industry found little interest in using the route for some years to come -- Byers said groups such as the council are influential lobbyists and their voice will be heard in international capitals.

"I'll be looking very closely to see if any nation state is prompted to take a position now that this industry association has," Byers said. "Is BIMCO raising the issue now, a prelude to the United States taking a position or worse yet, the European Union or Japan or China?"

Byers points out there hasn't yet been any international reaction to Canada's new Arctic shipping rules.

"The international jury is still out on this."