This case, now pending before Canada's Supreme Court, involves a speeding ticket issued to Roger Bilodeau, a lawyer, who by refusing to pay has broadened the legal challenge raised by Mr. Forest. Essentially, the first case centered on a claim that a law passed in 1890 establishing English as the sole official language illegally contravened the legislation that established Manitoba and that gave official status to French. In its decision, Canada's highest court upheld the supremacy of the earlier act.

The focus of the Bilodeau case, however, is the province's motor vehicle act and, by implication, every other law enacted here since 1890 and published solely in English. Fearful of the legal chaos that would result if Mr. Bilodeau's position were affirmed, the provincial government on Friday asked the court to suspend its deliberations while officials here seek a negotiated compromise with the French-speaking group. Mr. Bilodeau and the major groups in his community have joined in the request for an adjournment and have indicated they really want more assurances for the future use of French rather than a rewriting of past laws.

In his office at the legislature, Premier Howard Pawley explained that the ''looming consequences of a Supreme Court decision would be momentous, invalidating all our laws, and forcing them to be reenacted.'' He added, however, that the French-speaking community was being very reasonable and that it was not holding the government to ransom but was merely seeking its legal rights.

Across the Red River in the St. Boniface district, where the French speakers have lived for five, six and seven generations, the issue is seen in social rather than legalistic terms. ''What all this means is that we want it established that we are not just another so called ethnic group,'' said Gilberte Proteau, former president of the Society of Franco-Manitobans, a community development agency. ''The other groups that settled here, the Ukrainians, Germans, Jews and Italians, more or less knew what kind of society they were coming to. There was a trade-off in terms of the social contract and they were not seeking to recreate their homelands, though obviously they want to protect their cultures. This was not the case with us or the native peoples. We were here as a nation before there was a Manitoba.'' A Battle With Assimilation

Mrs. Proteau, who remembers going to school during and after World War II when all instruction in French in Manitoba schools was illegal, hopes that the recent legal victories will restore selfconfidence to a community that has grown frailer each year.