When President Trump told several Democratic congresswomen to “go back” to “the crime infested places from which they came,” he deployed language that the government uses as an example of workplace discrimination.

Trump’s remarks were widely interpreted to refer to four representatives, all women of color: Alexandria Ocasio-Cortez (D-N.Y.), Ayanna Pressley (D-Mass.) Rashida Tlaib (D-Mich.) and Ilhan Omar (D-Minn.) All except Omar were born in the United States.

Telling immigrants and people of color in the United States to “go back to their country” or “go back to where they came from” is such a well-worn, racist trope that has persisted throughout the country’s history, that the U.S. Equal Employment Opportunity Commission cites it in its guidelines for immigrants’ employment rights:

Ethnic slurs and other verbal or physical conduct because of nationality are illegal if they are severe or pervasive and create an intimidating, hostile or offensive working environment, interfere with work performance, or negatively affect job opportunities. Examples of potentially unlawful conduct include insults, taunting, or ethnic epithets, such as making fun of a person’s foreign accent or comments like, "Go back to where you came from, " whether made by supervisors or by co-workers.

The protection comes from Title VII of the Civil Rights Act of 1964, a federal law that protects workers from discrimination based on race, color, religion, sex and national origin.

“There’s no provision barring the president from saying certain things,” said Samuel Estreicher, a professor at New York University law school and director of its Center for Labor and Employment Law. But if an employee received such a remark in the workplace, he explained, “that could be evidence of national origin discrimination.”

Such was the case in 2007 when the U.S. Court of Appeals for the Fifth Circuit decided in favor of a plaintiff who had sued his employer, with the help of the EEOC, for discriminating against him because he was a Muslim born in India. In the lawsuit, Mohommed Rafiq alleged that his co-workers at a Texas car dealership began calling him “Taliban” and told him, “Why don’t you just go back where you came from since you believe what you believe?”

While these laws protect workers from discrimination by employers and are not immediately applicable in the case of Trump’s attacks on the U.S. representatives, the president’s words could nevertheless create complications for his agenda, attorney Michael T. Anderson said.

There are a lot of non-employment cases out there where Trump’s remarks are going to be smoking gun evidence of the true motivation of the chief executive,” said Anderson, who specializes in cases involving workers’ speech rights.

“If the president is sort of publicly advertising that he subscribes to a governing philosophy which is illegal under Title VII,” he said, “then any other kind of case, whether it’s a Muslim ban, census question, border crisis or anything else . . . the court has to consider that in understanding the main motivation of this presidency.”

So far, the main consequence for Trump has come in the form of a House resolution condemning his tweets, passed by a vote split along party lines.

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