God may or may not be on the side of unions, but a Catholic scholars group says that being on the other side, that is being against unions, is a “grave violation” of the church’s social doctrine. Opposing unions is, in fact, a mortal sin. And should be.

Anti-union actions violate both the letter and spirit of Catholic social doctrine, declared the Massachusetts-based Catholic Scholars for Worker Justice in a document distributed recently by the Catholic News Service.

Specifically, say the scholars, it violates church doctrine to try to block union organizing campaigns, stall in union contract talks, unilaterally roll back wages and benefits and violate existing labor contracts and other labor-management agreements.

Those tactics are far too commonly used against unions by far too many employers, including many who are Catholic and presumably follow church teachings. That’s not to mention the lay employers who operate Catholic hospitals and other facilities for the church and are openly ­ sometimes fiercely ­ anti union.

The Catholic scholars make an irrefutable case. As they say, Catholic social doctrine is “forthright and unambiguous ” in regard to unions. “It states boldly that they are essential to the universal common good.”

The scholars note that in supporting unions, the church is supporting the vital philosophical principle of freedom of association and the vital moral principle of “a just and or living wage.”

From the scholars’ point of view, it boils down to this: “The right to form unions is rooted in divine law,” and man-made law and the enforcement of it should reflect that. Opposing unions ­ that is, opposing the workers’ natural right of free assembly and right to decent wages and benefits – harms not only the workers directly involved. It also hurts society-at-large by lessening overall income and social solidarity and thus diminishing the universal common good.

The scholars’ statement stemmed primarily from concern over an increase in the use of anti-union tactics in recent years by some Catholic dioceses and Catholic organizations that obviously are not practicing what they preach.

“There are many Catholic institutions that live up to Catholic teachings,” said Joseph Fahey, a Manhattan College professor of religious studies who chairs Catholic Scholars for Worker Justice. “But there are some, either by ignorance or by design, that ignore Catholic teaching.”

Those who violate workers’ rights of unionization, added Fahey, “are involved in the grave matter of mortal sin.”

Fahey and his fellow scholars are particularly critical of the sponsors and managers of Catholic institutions who hire “union avoidance firms” to help them block their employees from unionizing or to help employers oust – or “bust” – unions that previously won the legal right to represent their employees on setting pay, benefits and working conditions.

Ousting or breaking unions in that way – or any other way – amounts to “wage theft” and “the theft of the human right of free association,” say the scholars.

Whatever your religion, or lack of it, you have to agree they’re absolutely correct. You have to agree there’s a great need for the spread of unionization to bring about the truly just society that the Catholic scholars, the nation’s union leaders and members and so many others of varying backgrounds seek.