Every year, hundreds of thousands of people enter wealthy countries on temporary work visas, hoping to earn a living and support their families. For many, those visas undoubtedly offer a chance to earn more money and build a more stable life. But for others, they become another source of vulnerability and abuse.

Consider the case of Larisa.

While browsing Facebook, she found an advertisement promising domestic work in Germany, a good salary and paid travel expenses. A mother of three from a remote village in Moldova, she left her children behind to chase that opportunity and lift her family out of poverty.

But when she arrived, the reality was very different. She was taken to a remote town, housed with other women and stripped of control over her documents. For a year, she says, she was forced to clean homes and care for elderly people for up to 20 hours a day without pay and under constant watch.

The International Organization for Migration later identified her case as an example of trafficking through a seemingly legitimate recruitment process. Her passport was confiscated, and she was not allowed to leave.

Larisa’s story is not unique. Across the world, migrants continue to be trapped in abusive working conditions not only by criminal networks but also by legal migration systems that leave workers dependent on a single employer.

Why legal migrants are vulnerable

Human trafficking is often associated with smuggling, border crossings or organised crime. But it can also affect legal migrants, often in less visible ways. It can involve debt bondage, confiscation of passports, restrictions on movement, withheld wages, threats of deportation and coercive working conditions.

Migrants are particularly vulnerable because they often arrive in a new country with limited resources, little knowledge of the local culture or language and no support network. Undocumented migrants are easy targets because they fear deportation and may avoid seeking help. But legal migrants can also find themselves trapped.

Many temporary work visa programmes tie workers to a single employer. If they leave that employer, they may lose not only their job but also their legal status. Contracts are often long, unclear or written in a language workers do not understand. Complaints can be met with threats, intimidation or warnings that speaking out will lead to deportation.

When legal systems enable abuse

In some cases, traffickers do not need to smuggle people across borders or forge documents. Weaknesses in legal migration systems make exploitation much easier.

Investigations into labour recruitment and labour leasing schemes in sectors such as agriculture, care work and construction have shown how migrants are promised legal jobs abroad in exchange for large sums of money, only to end up underpaid, threatened or trapped in unsafe conditions.

One of the most vulnerable areas is temporary visa programmes. In the United States, for example, investigations into the H-2A visa system, which is used to bring seasonal agricultural workers into the country, have documented wage theft, unsafe housing, withheld passports, restrictions on movement and dangerous heat exposure among seasonal migrant workers.

A Polaris analysis of labour trafficking cases reported to the US National Human Trafficking Hotline from 2018 to 2020 found that 72 percent of identified victims whose visa status was known held H-2A, H-2B, J-1 or A-3/G-5 visas. These temporary visa categories are commonly used for agriculture, seasonal labour, exchange programmes and domestic work.

The same Polaris research found that nearly half of labour trafficking victims whose immigration status was known were legally present in the United States on temporary visas.

These problems are not limited to one country or one visa system. Labour rights groups and international organisations have documented similar abuses across Europe, the Gulf and other regions that rely heavily on temporary migrant labour.

Debt, recruitment fees and passport confiscation

Debt is another way workers can become trapped.

Many migrants pay large sums to recruitment agents to secure jobs abroad. Families often borrow money, sell property or take out loans in the belief that the job will eventually provide stability.

But once workers arrive, the promised salary may be lower than expected, or the job may not exist at all. In some cases, workers are told they must repay inflated recruitment fees before they can leave or change jobs.

Similar patterns have been documented in Gulf countries, including Qatar, where rights groups have reported illegal recruitment fees, debt bondage, withheld wages and the confiscation of passports. Many workers arrive already in debt after paying large sums to recruiters. Others remain dependent on employers for their legal status and their ability to change jobs, making it harder to leave abusive situations.

What needs to change

Governments cannot claim to support legal migration while ignoring the ways legal migration systems can be abused.

Stronger oversight of recruitment agencies is essential. Agencies that charge illegal fees, make false promises or cooperate with abusive employers should face criminal penalties.

Workers should not be tied to a single employer. Visa systems should allow migrants to change jobs without immediately losing their legal status.

Governments should also ban recruitment fees charged to workers, strengthen labour inspections and create multilingual complaint systems so migrants can report abuse safely.

Whistleblowers must be protected. Migrants who report exploitation should not face detention or deportation, regardless of their immigration status.

Finally, governments should treat passport confiscation as a serious offence and provide legal aid and emergency housing for workers trying to escape abusive employers.

Larisa eventually made it home to her children. But many others do not.

As long as migrants remain tied to employers, burdened by debt and afraid of deportation, abuse will continue within systems that are supposed to protect them.

The views expressed in this article are the author’s own and do not necessarily reflect Al Jazeera’s editorial stance.