n256 Work is part of the original state of [humankind] and precedes [its] fall; it is therefore not a punishment or curse.
n257 Work has a place of honor because it is a source of riches, or a least of the conditions for a decent life, and is, in principle, an effective instrument against poverty.
n305 The Magisterium recognizes the fundamental role played by labor unions, whose existence is connected with the right to form associations or unions to defend the vital interests of workers employed in various professions.
n306 The Church's social doctrine teaches that relations within the world of work must be marked by cooperation: hatred and attempts to eliminate the other are completely unacceptable....Properly speaking, unions are promoters of the struggle for social justice....
n308 The modern socio-economic context, characterized by ever more rapid processes of economic and financial globalization, prompts unions to engage in renewal. Today, unions are called to act in new ways, widening the scope of their activity of solitdarity so that protection is afforded not only to the traditional categories of workers, but also to workers with non-standard or limited-time contracts, emplyees whose jobs are threatened by business mergers that occur with ever increasing frequency, even at the international level; to those who do not have a job, to immigrants, seasonal workers and those who, because they have not had professional updating, have been dismissed from the labor market and cannot be re-admitted without proper training.
Compendium of the Social Doctrine of the Church.
n2433: Access to employment and to professions must be open to all without unjust discrimination: men and women, healthy and disabled, natives and immigrants.
n2434: A just wage is the legitimate fruit of work. To refuse or withhold it can be a grave injustice. In determing fair pay both the needs and the contributions of each person must be taken into account.
n2435: Recourse to a strike is morally legitimate when it cannot be avoided, or at least when it is necessary to obtain a proportionate benefit. It becomes morally unacceptable when accompanied by violence...
Universal Catechism of the Catholic Church
Teachings and Important Documents of the Church concerning Work and the Rights of Workers
"Rerum Novarum" Pope Leo XIII 1891
"Quadragesimo Anno" Pope Pius XI 1931
"Mater et Magister" Pope John XXIII 1961
"Gaudium et Spes" Vatican II Council, 1966
"Laborem Exercens" Pope John Paul II 1981
"Centesimus Annus" Pope John Paul II 1991
Here is the link to the 2011 US Bishops annual statement on labor. http://www.usccb.org/about/domestic-social-development/upload/Labor-Day-2011.pdf