Liberal Leader Justin Trudeau's declaration that the federal party's new candidates must support pro-choice views does not faze his lone MP in Manitoba, who opposes abortion.

Trudeau announced this week that all candidates running for nomination to represent the Liberals in 2015 will have to support the party's pro-choice position.

The rule does not apply to current MPs, including Winnipeg North MP Kevin Lamoureux.

"The existing MPs … will be respected to a certain extent in their choices, but our position as a party is we do not reopen that debate," Trudeau said Wednesday.

Lamoureux says he is against abortion, but he will support the party leader's decision because he is a parliamentarian first.

"I don't want to see myself being defined as a one-issue member of Parliament," he told reporters Thursday in Ottawa.

"You can't change the way in which I feel and believe in regards to the issue of abortion," he added.

Maria Slykerman, who has organized anti-abortion rallies in Winnipeg for 14 years, says Trudeau's decree is not fair and makes the party "one-sided."

"All they want is for abortions to be legal and [they] don't care about the candidates or the voters," she said.

Slykerman said she expects about 1,000 people to attend this year's rally, which is taking place Saturday outside the Manitoba legislature.

Former MPs could be barred from running again

At least three former Liberal MPs across Canada could find themselves barred from running again for the party due to their staunch opposition to abortion.

Indeed, at least one — former cabinet minister Gar Knutson — told The Canadian Press he fully expects to be "red lighted" by the Liberal party.

Knutson had hoped to seek the party's nomination in Ottawa-Orleans, where Trudeau's hand-picked star recruit, retired general Andrew Leslie, is vying to carry the Liberal banner in the 2015 federal election.

At least two other former MPs — one-time minister Joe Volpe and veteran backbencher Dan McTeague — could similarly find their dreams of a political comeback shattered by Trudeau's new dictum.

As for how Trudeau's position could affect his party's standing in the polls, Raymond Hébert, professor emeritus of political science at the Université de Saint-Boniface, said he doesn't think there will be much impact.

"I'm not sure that it's really going to be a major issue for Mr. Trudeau," he said.

Hébert said the new Liberal leader has been trying to distinguish himself lately by making bold declarations, like when he kicked senators out of the Liberal caucus earlier this year.

With files from The Canadian Press