There's no "paper trail" on workers when they can't legally work. They're paid in cash, under the table. Shoddy work often results. In Berkeley in 2015, 6 Iris

There's no "paper trail" on workers when they can't legally work. They're paid in cash, under the table. Shoddy work often results. In Berkeley in 2015, 6 Irish students died when a shoddily-built balcony collapsed. No workers could be identified or interviewed because they were all "day labor". This is common in California. Search "slavery towers" for a current case in San Jose using all-illegal labor at "slavery" wages.