Plaintiffs noted that the mandate contains no exceptions for people who cannot get a vaccine or those who had COVID-19 and have recovered, as studies have shown they enjoy some protection against re-infection.
It also does not allow customers to choose instead to wear a mask or provide a negative COVID-19 test.
"It is against certain religious beliefs to inject a relatively unknown foreign substance into ones body. By mandating such a thing, the Mayor is essentially violating people freedom of religion," plaintiffs argued.
"Also, by mandating all employees of certain establishments to be vaccinated while knowing in is against certain groups religious beliefs, an argument could be made that the Mayor is in essence forcing employers to violate Title VII of the Civil Rights Act of 1964."
Plaintiffs also said the mandate doesn't make sense because it targets some businesses, such as gyms, but not others. That violates the Equal Protection Clause, the lawsuit asserts.
De Blasio told reporters in Manhattan on Wednesday that he has "tremendous confidence" that the mandate is legal. The city's law department declined to comment via email.