The landmark ruling last month said the ban is unconstitutional and gave Ottawa a year to rewrite it.
Judge Lynn Smith also granted an immediate exemption to the law, allowing Gloria Taylor, one of the women who brought the lawsuit, to die with a doctor's help.
In a statement, Nicholson said the government intends to seek a stay on all aspects of the ruling, including the exemption for Taylor, while it goes to the British Columbia Court of Appeal.
Taylor, a West Kelowna resident, suffers from Lou Gehrig's disease or ALS, and said she wants a doctor's help in dying with dignity before her illness progresses to the point that she can no longer care for herself.
"The government is of the view that the Criminal Code provisions that prohibit medical professionals, or anyone else, from counselling or providing assistance in a suicide, are constitutionally valid," Nicholson said.
"The government also objects to the lower court’s decision to grant a 'constitutional exemption' resembling a regulatory framework for assisted suicide."
Taylor hailed the lower court's ruling because it gives her control over when and how she dies.
She had hoped the government wouldn't appeal.
"I would really like to think that the government would see that they can't do this to me," Taylor said last month. "They can't do this to other Canadians.'
In her complex, 395-page judgment, Smith said the ban on physician-assisted suicide violates two sections of the charter of rights covering the right to equality and the right to life, liberty and security of the person.
She said the law must allow for doctor-assisted suicide in cases where patients have a serious illness or disability and are experiencing intolerable suffering. Such patients must ask for the help, must be free of coercion and cannot be clinically depressed, the ruling noted.
Nicholson, though, said the law has to protect people.
"The laws surrounding euthanasia and assisted suicide exist to protect all Canadians, including those who are most vulnerable, such as people who are sick or elderly or people with disabilities."
Nicholson also said the government would have nothing more to say on the matter while the case is before the court.
B.C. Civil Liberties lawyer Sheila Tucker, one of two lawyers involved in the case, said she's disappointed but not surprised by Ottawa's appeal of the case.
"We found the original decision to be extremely persuasive," she said.
The exemption in Taylor's case will stand until the appeal court decides otherwise, but Tucker wouldn't speculate on what the woman will do.
"Gloria's decision is an extremely personal decision, she's not going to make it based, I wouldn't think, on legal issues," she said.
"It is unfortunate that this may cause some stress for her in that process but it shouldn't in itself be a factor."
Reached at her home Friday, Taylor said she didn't wish to comment on the federal government's decision.
Last year, Taylor joined other plaintiffs — including a woman who took her dying mother to Switzerland in 2010 so she could end her life — in a lawsuit challenging Canada's ban on doctor-assisted suicide.
Besides Oregon and Washington state, Euthanasia and-or assisted suicide are also legal in other European countries including the Netherlands and Belgium.
Tucker said several Canadians have gone to Switzerland to get a doctor to help them commit suicide because unlike other jurisdictions, that country provides the service to non-residents.
Dr. Will Johnston of the Euthanasia Prevention Coalition of B.C., said he's pleased with the government's decision to appeal the ruling, which he called "logically inconsistent," for the sake of all Canadians.
"(Justice Smith) finds the right to suicide out of the fact that suicide is not a crime and this is questionable logic because there are many undesirable things that are not crimes, that the state should have no interest in encouraging," he said. "Suicide is one of them."
"The fact that some people are so dissatisfied that they choose to kill themselves is a tragedy but it's no reason to remove all of the protections in law for the rest of Canadians."
He said there's a risk of assisted suicide laws being abused by people who stand to gain financially from the death of elderly relatives, for example, and that measures to prevent such cases haven't worked in other jurisdictions.