A constitutional challenge of new sick leave rules for federal public servants that was to begin Thursday in an Ottawa court has been postponed until March.

It's just one of many legal challenges that may end up shelved now that Stephen Harper's Conservatives have lost power.

In fact, sorting out which battles to fight and which litigation to delay, reroute or drop will have federal Justice Department officials working like busy air traffic controllers this fall.

"Certainly the courts are of the view that we shouldn't be wasting their resources if we don't have to," constitutional lawyer Paul Cavalluzzo said Tuesday.

Cavalluzzo is lead counsel for a charter challenge against the Conservatives' sweeping anti-terrorism law, Bill C-51. It received royal assent in June, but the newly elected Liberals campaigned on amending the deeply controversial law.

"It would seem to me that in light of the fact there is a significant chance that this government will repeal all or most of Bill C-51, I'm hoping to sit down with government lawyers and perhaps consider putting this litigation on hold, pending decisions made by the government," Cavalluzzo said.

He might have to get in line.

Prime minister-designate Justin Trudeau won election last week promising to fix or flush a number of contentious Conservative laws. His pledges range from repeal of a bill that permits stripping convicted terrorists of their citizenship to looking at the government distribution of medical marijuana and re-examining some mandatory minimum sentences.

The Conservatives came to office with an approach to criminal justice, security and citizenship that "has been fairly uncompromising," says Carissima Mathen, who teaches constitutional law at the University of Ottawa.

"And that's really where it's run into trouble, because in a constitutional democracy, the government has to balance interests."

Justice file 'challenging' portfolio

She predicts justice will be a very challenging portfolio in the new Liberal cabinet.

"I will confidently say that, while the general issue is one that every incoming government faces, the scale of pending challenges and new legislation that has been targeted as constitutionally suspect, the sheer scale is unprecedented," said Mathen.

Trudeau has said he'll swear in his first Liberal cabinet next week. The new justice minister can expect the phone to start ringing immediately.

Constitutional lawyer Rocco Galati is currently appealing a lower court ruling on his challenge to Bill C-24, the law that empowers the cabinet to strip convicted terrorists of their citizenship. It's one of two charter challenges to the law, which Trudeau has promised to repeal.

"As soon as Prime Minister Trudeau convokes his cabinet I'm going to send them a letter and ask," Galati said Tuesday.

"I'm not holding my breath. My appeal is going to be heard in January. If he's going to repeal it before January, great. If not, I don't know."

Signs of a litigation thaw may have begun already.

This week, the Federal Court of Appeal was to begin hearing the government's appeal of a court ruling that overturned Conservative changes to refugee health coverage. Instead, the case was adjourned for two months at the government's request.

And the Professional Institute of the Public Service of Canada, the union representing civil service professionals such as lawyers, engineers and accountants, says its challenge to the constitutionality of arbitrary changes to collective bargaining imposed by the Harper government was to begin hearings Thursday, but has been rescheduled to March.

The union challenge isn't the only one related to the Conservatives' last omnibus budget bill, known as C-59.

Federal information commissioner Suzanne Legault has taken the government to court over C-59 changes that retroactively absolved the RCMP of alleged wrongdoing in the 2012 destruction of long-gun registry data.

That could be one of the trickier decisions, politically, for a new government to reverse. The Ontario Provincial Police dropped its investigation this fall into RCMP wrongdoing as a result of Bill C-59. Do the Liberals rewrite the law, effectively legislating the Mounties back under a police investigation, or defend the controversial provisions and let the courts decide?

Pending litigation

Other pending litigation may be more easily resolved.

The information commissioner is also taking the Prime Minister's Office to court over its refusal to release documents related to four senators embroiled in scandal.

And the Conservative government last month launched a mid-election, Hail Mary appeal bid to the Supreme Court of Canada over its failed regulations prohibiting facial coverings at citizenship ceremonies.

Mathen notes that former prime ministers have had tough court rulings that greatly complicated their political agendas. Brian Mulroney had to deal with the Supreme Court abortion ruling in the Morgentaler case. Jean Chretien faced aspects of the country's child pornography laws being struck down.

Yet neither government had as acrimonious a relationship with the courts as Harper's Conservatives.

In the constitutional legal community, "for the most part, there's anticipation of a much more positive tone vis-a-vis both civil liberties, the charter and the courts," said Mathen.

"But also I think there's some apprehension at the scale of the task that this government will face."