A Canadian rule now requires that ships built after 2008 must have a filtration system - that cleans water ships take onboard to account for changing cargo loads.
The six American vessels immediately affected by the rule have applied for a 5-year exemption.
Jim Weakley is with a lobbyist group that represents the interests of American shippers in the Great Lakes. He calls the rule a "regulatory embargo."
"That creates opportunities for Canadian flagged ships to steal that cargo from the Americans, which in my biased opinion, was the goal of the Canadian industry."
Canada's transportation department says the rule is fair and will prevent an estimated 34 invasive species from being introduced and spread in their waters.
