Due process is a requirement that the government respect the rights due a person or organization under the law and isn't really relevant here, as the government

Due process is a requirement that the government respect the rights due a person or organization under the law and isn't really relevant here, as the government isn't taking direct action and a private business has the right to not do business with anyone they want. Also, a subpoena is a written order to compel testimony or evidence. I think you mean a court order.