Aboriginal Affairs wrote to a number of First Nations last month to advise them they have until Wednesday to publish their financial information online.
If they don't, they will find themselves on a list of delinquents that the department plans to publish on its website on Thursday.
That's one of the milder outcomes. Equally tame is a requirement that First Nations come up with a list of all the steps they need to take in order to prepare and publish their financial information.
But Aboriginal Affairs is also warning it could come down a lot harder on those First Nations that don't comply with the new law.
One of those actions could be to order third-party managers to withhold band councillors' pay.
Or Aboriginal Affairs could notify other departments, those with which the First Nations have funding agreements, of their non-compliance — presumably so those organizations could take actions of their own.
The department has also told First Nations it is prepared to go to court to get them to publish their financial information.
Tony Wawatie, interim director general of the Algonquins of Barriere Lake in western Quebec, said his First Nation — which is already under third-party management — is being squeezed even further by Aboriginal Affairs.
"It's blackmail," Wawatie said.
"The way I see it, it's blackmail, because what can (Aboriginal Affairs) do any lower? Are they going to put us in double third-party management? What are the other steps? We've hit as far as we can hit."
Other First Nations in western Canada say they plan to resist any attempts to get them to comply with the financial-transparency law.
"This tactic is designed to force local compliance to an unjust law by denying families access to essential programs and services," First Nations from Treaties 4, 6 and 7 said in a news release.
"Not only is C-27 a breach of our historic treaty relationship, it is a denial of our international right of self-determination as indigenous nations. In no other place in Canada do such oppressive conditions exist under the coercive force of the federal government than Indian reserves."
Aboriginal Affairs Minister Bernard Valcourt's office said the law "applies the same principles of transparency and accountability to First Nations governments that already exist for other governments in Canada."
"First Nation band councils are expected to comply with the disclosure provisions in the First Nation Financial Transparency Act," spokeswoman Erica Meekes wrote in an email.
"Bands which failed to comply by the deadline — which was July 29, 2014 — will receive several formal reminders. After 120 calendar days, if there is no resolution, for bands that are refusing to comply with the law, the government will take action according to the provisions of the law, which could include withholding of funding."
Liberal MP Carolyn Bennett criticized the government's approach.
"There is a way of getting at this transparency and accountability," she said in an interview.
"Unfortunately, this government chose to ram through a bill that everybody disagrees with and this is what happens. People react and say, 'Nothing about us, without us'."
The Conservative government's First Nations Financial Transparency Act required First Nations to post audited financial statements and information about the salaries and expenses of chiefs and councillors on a public website within 120 days of the end of the financial year ending March 31, 2014.
They had until July 29 to do so. By mid-November, 477 First Nations had complied.
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