n this picture taken late July 11, 2017, migrant workers sit amidst Malaysian immigration officials in an open field following a raid at a construction site in Port Dickson. Malaysia's immigration department is carrying out a nationwide crackdown on illegal foreign workers after a deadline for registration expired on June 30. Manan Vatsyayana | AFP | Getty Images

Malaysia is already cracking down on undocumented immigrants — and they may be getting ready to arrest a lot more. So far, the country has arrested more than 3,300 workers and 84 employers since July 1. Activists are crying foul over possible abuses of rights, and business owners are also speaking out against what they say are unfair rules that could cripple industries. The nationwide raid began a day after the deadline passed for migrants to register for an Enforcement Card (E-Card), which allows those lacking valid permits to work in the country until February 14, 2018. If an undocumented migrant is found without an E-Card, they are detained.

20-30% of the workforce

This month's crackdown is not Malaysia's first. Over 146,000 undocumented workers have been detained in 26,870 enforcement operations between 2014 and 2016, Malaysian news agency New Straits Times reported. The frequent and sustained crackdowns point to the lack of a long-term migration policy that responds to employers' needs for migrant labor, according to Anna Olsen, technical specialist at the International Labour Organization, a United Nations agency. According to Foo Chek Lee, president of construction and building organization Master Builders Association of Malaysia, each crackdown further diminishes the already-thin labor supply and increases the cost of wages, making it more difficult for construction companies to survive. And Malaysia's construction and plantation industries came to a standstill when mass migrant crackdowns occurred previously, Joseph Paul, program officer at Malaysian human rights organization Tenaganita, told CNBC. Estimates suggest that there are three to four million migrants currently employed in Malaysia, which would constitute approximately 20 to 30 percent of the country's workforce. The brewing crackdown could conceivably mean hundreds of thousands of those workers are arrested and deported.

The registration problem

Although the E-Card system was open to many migrants, the problem for them was that all applications needed to be submitted by employers. And for a variety of reasons, that might not have happened. "It is unfair that a worker is arrested for something that he cannot on his own do," Paul said Migrant workers are also often mistreated in such raid operations, according to Olsen.

Migrant workers wait for their work permits to checked by Malaysian authorities following a raid at Port Dickson, Malaysia, on July 11, 2017. Manan Vatsyayana | AFP | Getty Images

Civil society actors have also expressed concern about the long-standing cramped, unhygienic conditions at Malaysia's detention centers. Over 100 people have died in these centers in the past two years, according to Reuters. In comparison, the U.S. recorded 10 deaths in its immigration detention system, which holds many more detainees, in the last financial year. And although migrants often face unpaid wages, an undocumented worker who has been detained cannot seek redress on that front, Paul said. That's just one of the ways the crackdown is affecting their livelihoods. "In times of crackdowns, migrant workers risk being fired by their employers, which can lead to irregular status or loss of wages," Olsen said. "Other employers … might try to 'hide' irregular migrant workers, contributing to further isolation and increased risk of exploitation."

The business perspective