The measure would see national security agencies tracking Canadians who travel to those areas and force those returning home to prove they were in the region for humanitarian reasons, or as journalists covering the conflict.
At a campaign stop in Montreal, Trudeau said Prime Minister Stephen Harper has failed to justify what would amount to limitations on Canadians' rights.
"Canada is a country that respects people's rights,'' Trudeau said as he kicked off his Quebec component of the federal election campaign.
"And any time a government chooses to limit those rights, it has to be able to answer very direct and complete questions about why it's necessary, about how it will work, about what the clear plan is and Mr. Harper has done none of that.
"For us, it's a piece of electoral posturing.''
Trudeau and NDP Leader Tom Mulcair have previously taken aim at Harper over civil liberty questions arising from the Conservatives' controversial anti-terrorism law, Bill C-51.
The Liberal leader also focused on Harper's economic policies on Monday, saying the travel ban was simply a Conservative attempt to distract from their failure to create jobs and a better life for middle income earners.
"Mr. Harper is obviously desperate to talk about anything other than the failure of his economic plan,'' Trudeau added. "Everywhere I go across the country, Canadians are worried about their retirements, they're worried about their kids and their kids' future.''
Trudeau's party hopes to siphon support from the NDP in Quebec between now and the Oct. 19 election.
The Liberals had only seven of 75 seats in the province at dissolution, compared with 54 for the NDP.
Part of Trudeau's strategy over the next 10 weeks will be to portray Mulcair as someone whose policies do not resonate with Quebecers.
On Monday he cited the NDP plan to implement a national daycare program as one example, saying an extensive child-care system already exists in the province.
"Quebecers are tired of Mr. Harper and they need a new prime minister,'' Trudeau said. "That is the clear desire.
"The choice that Quebecers are going to have is someone who says nice th
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