Today we received an email that said that all Canadian employees need to submit a request 2 weeks prior to any statutory holiday to our managers for approval. We are salaried employees. Is it legal to deny our Statutory Holidays without us agreeing to it?

By default, most Ontario employees are entitled to take statutory holidays off of work and still receive holiday pay (see https://www.ontario.ca/document/your-guide-employment-standards-act-0/public-holidays#section-1). However, there are some workplace or industries were an employee may be required to work statutory holidays, for a variety of reasons, in which case they would receive premium pay (time and a half pay). For matters such as holiday pay, vacation pay or overtime pay, it would be useful to contact the Ministry of Labour in Ontario if you have any further questions or concerns regarding the company's policy. For matter such as termination, severance, or significant changes to your employment, employees should consult an employment lawyer, rather than the Ministry of Labour.