English only rules always bring controversy, even at a bookstore in New Haven, Connecticut, very near Yale university.  The EEOC generally frowns on such rules, but allows them for "business necessity."   In this case, the book store is essentially claiming the customers are uncomfortable with employees speaking Spanish.  Does the comfort of customers count as a business necessity?  Maybe, according to Workplace Prof.  It depends on whether there is evidence of discriminatory motivations.  That means an employer seeking to implement such a policy needs to show something more than mere perception of what makes a customer happy.  

It would also help to show some safety issue.  ….  Safety at a bookstore?  Those paper cuts can be viscious…..