A group of 500 workers at the Trump International Hotel in Las Vegas voted to unionize in December and have been demanding a sit-down and contract negotiation with the management. The National Labor Relations Board has certified this union over the objections of Trump's Company. The management has announced their intentions to appeal the ruling, and workers have reported being intimidated by members of a "union avoidance" consulting firm hired by the management. The firm told them that if they voted to unionize they'd lose their jobs, and that the company would blacklist their names so that they'd never find work in Las Vegas again.
The National Labor Relations Act prohibits companies from using coercion and intimidation tactics in order to prevent employees from unionizing. The reason these workers were unionizing was because of their low wages--"lower than most in Las Vegas" according to the housekeeper who organized the union. Trump likes to talk about the problems faced by many (white) Americans working for lower-wages (and how it's Mexico's fault that wages are falling), but his own businesses routinely engage in practices that lower wages and the standard of living for workers.