The latest spat, the second in recent weeks between the federal government and a branch of the UN, also sparked debate over who is responsible for the growing divide between Canada and the world body.
United Nations High Commissioner for Human Rights Navi Pillay said Monday she found the controversial Quebec law to be part of an alarming trend.
The law sets rules for gatherings of more than 50 people, requiring organizers to provide eight hours' notice of the itinerary and length of the event.
Pillay expressed her opinion of the Quebec law in a single paragraph of a long speech in Geneva during which she lamented rights violations in places such as North Korea, Zimbabwe and South Sudan.
"Moves to restrict freedom of assembly in many parts of the world are alarming," she said.
"In the context of student protests, I am disappointed by the new legislation passed in Quebec that restricts their rights to freedom of association and of peaceful assembly."
Quebec Premier Jean Charest called it rich that the criticism came from an agency based in Geneva, a city with its own much tougher protest laws.
"It's ironic ... that they're criticizing a law that requires eight hours' notice before a protest and an itinerary, when in Geneva — where the United Nations office is — it's 30 days' notice that they require," Charest told reporters at the global environmental conference in Rio de Janeiro.
"So we're not as severe as the place that hosts the United Nations. We're more supple, and more permissive."
The Conservative government swiftly defended Quebec's right to pass its own laws in a democratic environment.
Industry Minister Christian Paradis, the government's Quebec lieutenant, took Pillay to task for avoiding other, more serious human rights abuses in places such as Sri Lanka, Iran and Belarus.
Foreign Affairs Minister John Baird also said he was disappointed Pillay mentioned Canada.
"Quebec is a very democratic place, subject to the rule of law," Baird said. "People can challenge the government's decisions in court so I stand behind the government of Quebec.
"With what's going on in Syria, with what's going on in Iran and Belarus, the UN would be better to spend its time on there."
The government recently shot back hard at the UN's special rapporteur on the right to food for accusing Canada of ignoring hunger within its own borders.
Baird wouldn't say whether he saw a trend, but noted: "If people around the world enjoyed the human rights that people in Canada and especially Quebec enjoyed, this world would be a much better place."
The NDP's foreign affairs critic Paul Dewar said Monday the latest clash between the Tories and the UN was part of a "dangerous trajectory" that dates back to Canada's historic failure to win a temporary two-year term on the powerful security council two years ago.
"We're losing our credibility. We need to earn back our seat at the security council. This is not how you do that," said Dewar.
"It's a little bit cute by half when you have a government (that) on the one hand says the UN is important for things like Libya, but on the other hand — when there's any critique of Canada at all — it has no time."
Dewar said the recent musings by Tory backbencher Larry Miller that Canada should quit the UN was also troubling.
But a Geneva-based non-government organization leapt to Canada's defence, saying Pillay made a "big mistake" targeting Canada while ignoring the repression of Tibetan Buddhist monks by China, for instance.
"When a prosecutor goes after jaywalkers while allowing rapists and murderers to roam free, that’s not only illogical, but immoral. She just needs to keep things in proportion," said UN Watch director Hillel Neuer, a Montreal-born lawyer.
"The Canadian activists who presumably put her up to this are misguided, and the UN commissioner is making a big mistake by sending the message that countries that have blots on their system — if indeed the Quebec law is a blot — are even worse than countries where the blot is the system."
Canada also faced criticism two weeks ago when the UN Committee Against Torture accused it of being "complicit'' to human rights violations committed against three Arab-Canadian men held in Syria after 9-11.
The government didn't directly respond in that case, but federal lawyers essentially did just that in the course of defending a lawsuit brought by one of the men over his imprisonment and torture in Syria.
In his main address to the UN General Assembly last fall, Baird criticized the institution for essentially turning a blind eye towards the behaviour of some more despotic countries.
Baird was particularly irked that some countries with dubious rights records are allowed to hold memberships on, or occupy the chair of, major committees.
In signs of protest over the last year, Canada has boycotted North Korea's rotating presidency of the UN conference on disarmament and Iran's vice-presidency of the General Assembly and its seat on the commission on population and development.
Most recently, Canada took a pass on the UN's world tourism office because it recognized Zimbabwe's dictator Robert Mugabe.