You're free to assign employees based on their foreign-language ability. For example, you can assign bilingual Spanish-speaking employees to serve customers who speak Spanish.
But remind managers not to overstep employees' job descriptions or rely too heavily on bilingual employees over other workers. That could include, for example, requiring bilingual retail employees to spend more time on the floor than their co-workers, or preventing your sole bilingual customer service phone rep from taking standard breaks.
To avoid legal trouble, analyze whether you assign duties to bilingual employees outside their job descriptions simply because of their national origin.
If you assign duties to employees based on a protected characteristic (race, gender, national origin, age, etc.), make sure the assignment is consistent with company policy and you apply it fairly.
Recent case: Undercover police detective Felipe Arroyo complained to his supervisors that he was assigned excessive and more dangerous work, including drug buys, than his peers because he spoke Spanish. He filed suit, claiming that the added duties amounted to discrimination based on his national origin.
A jury sided with Arroyo, awarding him $425,000 on his discrimination claim. (Arroyo v. San Diego, No. GO33356, CA 1/4, 2004)
Final tip: Counsel supervisors that if they must assign bilingual employees to different or additional work, it's wise to update their job descriptions and even consider additional pay for bilingual skills.