From the prisons of Iran to the ports of California, the cry went out Friday—let workers organize. International Human Rights Day, observed on Dec. 10, increasingly is an occasion to recognize labor rights as a distinctive, critical part of human rights, as recognized in the Universal Declaration of Human Rights and other international covenants. More than rights to freedom of speech or religion, the rights of workers combine collective and individual rights. Freedom of association—the right of workers to form unions, to bargain collectivelyand to take action such as strikes—is the precondition for the exercise of individual rights as workers.

We’re accustomed to governments and employers denying those rights in many less-developed countries. So it may outrage but not surprise manypeople when Amnesty International calls for urgent action in support of Reza Shahabi, the treasurer of the independent Tehran bus drivers’ union, who is on a hunger strike in Evin Prison protesting his arrest for organizing a union.. The Iranian government is holding several other leaders and members of the influential bus union for asserting their right to unionize, making them “prisoners of conscience,” according to Amnesty International.

Multinational companies operating in developing countries are often equally complicit with repressive governments in denying workers their rights. This year the International Labor Rights Fund (ILRF) named five companiesor business groups as the “worst companies of 2010 for the right to associate”—the Bangla Desh Garment Manufacturers and Exporters Association, Chiquita Brands International, Dole, Del Monte, and RJ Reynolds Tobacco Company.

For example, ILRF reports, banana workers in Chiquita’s Guatemalan subsidiary, Cobigua, have endured years of threats of job loss or violence as they have tried to organize—threats that are chilling in a country where 43 union leaders or members have been killed because of their union work. The company often pays less than the minimum wage or deprives workers of social security, at times using homework, subcontracting or other manipulations of the employment relationship to frustrate organizing and drive down wages. And in the two instances where workers negotiated a contract, the company has threatened to close operations if workers don’t accept freezes or cuts in wages and benefits.

Among developed countries, the United States has the worst record on protecting labor rights, with a combination of extraordinarily anti-union businesses and weak labor laws, often weakened further by conservative court rulings on such basics as the right to strike, as Rutgers University law professor James Gray Pope has argued.

Compared to most European countries many groups of American workers are simply excluded from protection of labor laws—and businesses exploit those loopholes.

Take the case of Will Cantwell, who drives a truck delivering goods from the port of Oakland, California, to warehouses and shipping destinations. He is considered an independent contractor, not an employee, because he owns his own truck and is responsible for maintaining it. But he works—exclusively, at the company’s insistence—for a shipper who unilaterally sets his payment by the load and sets his schedule, which always involves long hours of unpaid waits for a new assignment. He has no health insurance or retirement plan with his job, and given the hours he works and costs for his truck, he says he often earns less than the minimum wage. He and fellow port drivers have no right to organize under U.S. law. “Things look pretty grim,” he says. “The situation is inexcusable.”

The National Employment Law Project reaches the same conclusion in a new report, The Big Rig: Poverty, Pollution, and the Misclassification of Truck Drivers at America’s Ports. Port drivers are not really independent contractors, but their misclassification “drives the economics of the port trucking industry” and endangers public health and safety as well as the environment, the NELP study concludes.

“Misclassification of employees as independent contractors drains public coffers of tax dollars, strips workers of important protections and benef its, and undercuts companies that play by the rules,” it says. And because workers earn so little—netting on average around $10 an hour—they cannot afford to maintain their old trucks properly or buy new ones. Consequently they pollute the neighborhoods around the ports, endangering residents’ health.

But many other workers are also excluded deliberately from labor law protections, not just by misclassification. The Excluded Workers Congress, formed last summer at the U.S. Social Forum in Detroit, catalogs many of these workers’ problems in a new study, Unity for Dignity: Expanding the Right to Win Human Rights at Work.

They advocate full organizing rights and labor law protection for domestic workers, farm workers, taxi drivers, restaurant workers (tipped workers have lower minimum wage standards but can organize), day laborers, guestworkers, workfare workers, ex-prisoners (who are often forced on employment applications to reveal their incarceration, even after serving their punishment), and workers in right-to-work states. The list could even be longer, for example, including professors and graduate teaching or research assistants at private universities.

Some of these exclusions historically reflect efforts to exclude occupations dominated by black workers, such as farm or domestic work, but these are also growing categories of workers, who are abused and typically poorly paid.

But these workers are organizing, sometimes with allies (like environmentalists and community groups supporting port truckers). And they’re winning victories, such as a Domestic Worker Bill of Rights in New York state.

The battle for human rights for these excluded workers may still be long and hard, but it has at least begun.