Brian Casey told Nova Scotia Supreme Court the regulator went too far in April when it decided it would ban graduates from Trinity Western University from the province's bar admission program unless the school dropped a requirement that students abstain from sex outside heterosexual marriage.
The requirement, spelled out in a pledge that all students sign, has been criticized as discriminatory against gays and lesbians.
Casey argued the law society has jurisdiction over its membership in Nova Scotia, nothing more.
"The barristers' society has no authority to refuse a student because of the school's conduct," he told the court, which is scheduled to hear the case until Friday. "They don't even claim that they have the authority to approve a law school."
Casey went on to suggest the court should overturn the law society's regulation on the grounds that it infringes on future students' charter rights of freedom of religion, freedom of expression and freedom of association.
He said Judge Jamie Campbell has to decide whether those rights are in conflict with the right of individuals not to face discrimination on the basis of sexual orientation.
Casey argued there is no conflict because the law society has failed to produce evidence that the proposed law school in Langley would harm anyone in Nova Scotia.
"The question is, what does the barristers' society need to show before they can justify infringing on rights?" Casey asked outside the court. "The answer is they need to show specific harm. They don't claim that there's specific harm here. What they say is that people are going to be uncomfortable. That's not enough."
However, the judge said it appeared the law society was arguing that if it accepted articling students from a school that promoted discriminatory behaviour, that could lead to stress in Nova Scotia's gay community. Casey said there was no proof of that before the court.
Casey also said the Charter of Rights and Freedoms doesn't apply to private institutions or any university for that matter.
"This is really the key issue in the case," he said outside the court. "In Canada, only governments are subject to the charter."
Since the law society, as a quasi-legislative body, must adhere to the charter, it is required to remain neutral when deciding who can be admitted.
"It's not entitled to promote one view of marriage over another," Casey told the court.
He said the courts have also affirmed that religious groups have the right to exclude others in their efforts to define themselves.
However, he stressed that the university, which hopes to open its law school in 2016, welcomes gay and lesbian students so long as they sign the school's community covenant.
"Trinity Western doesn't ask about sexual orientation," Casey said. "It's not that we have cameras in the bedrooms."
No students have been expelled from the university since it started operating more than 50 years ago, he said.
The barristers' society has said its decision to deny accreditation would prevent graduates from Trinity Western from articling in Nova Scotia, but it wouldn't stop them from practising law in the province.
In its court brief, the society says it has not violated the rights of the law school's future graduates.
"While the charter does protect freedom of religion and association, it does not require the society to validate or support conduct that discriminates against others," the brief says.
"Those who hold evangelical beliefs are not singled out (by the society's decision). Instead, it is the law degree from the schools that engage in discriminatory conduct that is singled out."
Earlier this month, the British Columbia government revoked its support for the law school, saying the university can't enrol students in the program because of the "uncertainty" over approval by the B.C. Law Society.