The case was scheduled to proceed today but a spokeswoman for one of the student federations contesting the law says logistical reasons forced the delay.
Lawyers representing the student federations and other groups will be in Quebec Superior Court seeking to have certain parts of Bill 78 suspended.
It's one of two legal motions filed last week against the emergency law adopted earlier this month to crack down on recent student protests.
The first motion seeks to suspend sections of the law that involve public protest.
The second motion is to have Bill 78 declared invalid altogether and it will be heard at a later date.
The government argues the law preserves the rights of students to attend school, while also respecting free speech.
It lays out rules for demonstrations, such as ordering assemblies of more than 50 people to give eight hours' notice of the protest route and the estimated duration of the event. It also sets hefty fines for those who contravene the law.
So far, Bill 78 has been used sparingly by police across the province. It may even have backfired politically, in that protests against the government have grown larger, attracted more diverse crowds and spread to different cities.
Polls have suggested Quebecers are actually divided in their opinion on the legislation.
The groups mounting the legal challenge say the law severely restricts the fundamental rights of citizens. The student groups, labour federations and a wide range of other organizations claim the law is unconstitutional and a violation of basic rights.
Student leaders have described the legal motions as the biggest constitutional challenge in the history of Quebec.
Bill 78 was introduced two weeks ago while talks between the provincial government and the student leaders appeared at an impasse. After two tumultuous weeks, the sides returned to the negotiating table on Monday.
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