OTTAWA — Prime Minister Justin Trudeau took the rare step of declaring a national public order emergency on Monday in a push to end protests that have paralyzed the center of the Canadian capital for more than two weeks and reverberated across the country.
Mr. Trudeau and several of his cabinet ministers said the move would allow the government to take a variety of steps, including freezing bank accounts of protesters, to clear the blockade of about 400 trucks in Ottawa and smaller protests that have closed border points in Alberta and Manitoba.
“We cannot and will not allow illegal and dangerous activities to continue,” the prime minister said in a speech to the nation, pointing to“serious challenges to law enforcement’s ability to effectively enforce the law.”
The invocation of the Emergencies Act confers enormous, if temporary, power on the federal government.
It allows the authorities to move aggressively to restore public order, including banning public assembly and restricting travel to and from specific areas. But Mr. Trudeau and members of his cabinet offered repeated assurance that the act would not be used to suspend “fundamental rights.”
It has been half a century since emergency powers were last invoked in Canada. Mr. Trudeau’s father, Prime Minister Pierre Elliott Trudeau, imposed them during a terrorism crisis in Quebec. Monday was the first time that the 1988 Emergencies Act has been used.
The response by the police and all levels of government to the crisis, which included an almost weeklong blockade of an economically critical border crossing with United States, has been widely criticized as inadequate. Mr. Trudeau, some critics contend, should have intervened earlier and perhaps even deployed troops to break up the protest.
On Monday, Mr. Trudeau said he would not use his authority under the declaration, which will last for 30 days, to bring in the military, reiterating his previous position against intervention by the armed forces.
But Canada’s justice minister, David Lametti, outlined a wide array of special powers now at the government’s disposal.
The police will now be able to seize trucks and other vehicles used in blockades. The measure will formally ban demonstrations that “go beyond lawful protest,” he said, and the government will formally ban blockades in designated areas like border crossings, airports and the city of Ottawa.
Tow-truck operators, who have been reluctant to cooperate with the police, will now be compelled to work with law enforcement agencies to clear Ottawa’s streets and the border crossings at Coutts, Alberta, and Emerson, Manitoba.
While the Royal Canadian Mounted Police, the national force, will not take over policing in Ottawa from that city’s municipal service, its members will now be allowed to enforce provincial laws and local bylaws and carry out any federal orders made under the Emergencies Act.
Chrystia Freeland, the deputy prime minister and finance minister, outlined several measures that include expanding money laundering and antiterrorism powers to control the online crowdfunding platforms that have helped finance the protests. Credit card processors and fund-raising services will be required to report any blockade-related campaigns to Canada’s anti-money laundering agency.
The police will be exchanging information with banks about protesters, and their personal and business accounts may be frozen. Insurance companies will be required to revoke insurance on any vehicles used in blockades.
“Send your semitrailers home,” Ms. Freeland told protesters.
Mr. Trudeau promised that the government would soon announce financial assistance for stores, restaurants and other business in Ottawa that have been forced to close because of the occupation.
On Monday morning, as Mr. Trudeau was outlining his decision with the premiers of Canada’s 10 provinces, the Mounties said that a large cache of weapons, including guns, body armor and a machete, had been discovered in three trailers at the Coutts border blockade.
When the elder Mr. Trudeau declared an emergency nearly 52 years ago, he relied not on the law his son used Monday but on a predecessor, the War Measures Act, and his challenge was not civil unrest but terrorism. A group of Quebec separatists, who had conducted a bombing campaign in Montreal, had kidnapped Quebec’s deputy premier and a British diplomat. Pierre Laporte, the deputy premier, was later assassinated.
On Monday, several national security experts praised the current prime minister’s decision.
“The Emergencies Act was necessary in the face of the breakdown of law and order in parts of Canada and the economic and reputational costs that Canada suffered with some of its allies, particularly the United States,” said Wesley Wark, a national-security expert and a senior fellow at the Center for International Governance Innovation, a Canadian public policy group. “I expect some stepped-up law enforcement in the next couple of days.”
Leah West, a professor who studies national security law at Carleton University, said she believed some of the restrictions on rights introduced by the law, like those on movement, are acceptable under Canada’s Charter of Rights and Freedoms. But she said the financial measures may be more problematic.
Many Canadians, and Ottawa residents in particular, have shown increasing impatience over what they view as an anemic police response to the protests, which began as a truck convoy in the western province of British Columbia and reached the capital on Jan. 29. While there has been little physical violence, lives in the areas surrounding the Parliament have been disrupted and the police are investigating several complaints of hate crimes and harassment.
Protesters, whose numbers swell on weekends, have desecrated the national war memorial, and legal violations like public drinking are widespread. An upscale shopping mall just blocks from Parliament is now into its third week of closure. Stores there have lost tens of millions of dollars in sales and about 1,500 workers lost wages.
Peter Sloly, the police chief of Ottawa, has repeatedly said that his force, which had jurisdiction over the protests until the emergency declaration, is outnumbered and asked for upward of 1,800 more officers.
But on Sunday, Bill Blair, the federal emergency preparedness minister and a former police chief of Toronto, said he found the lack by action by Ottawa’s force “inexplicable.”
As the law requires, Mr. Trudeau gathered Canada’s 10 provincial premiers to inform them of his decision on Monday, as well as his caucus and cabinet. While the emergency declaration went into effect immediately, the House of Commons must approve it within seven days.