The short answer is yes.
In Ontario, under the Employment Standards Act (ESA), employers are entitled to choose when an employee can take their vacation time. Employers may schedule vacations and require employees to take vacation time when it suits the needs of the workplace.
An employee may also be able to use vacation days, sick days or banked overtime instead of taking unpaid time off.
With respect to COVID-19, the Ontario government has implemented job-protected leaves. You can learn more about this here.
With the above being said, if an employer does not have a history of ordering when an employee can go on vacation, the employee may be able to argue that the employer does not have a right to do so accordingly to the terms of employment (i.e. either as a result of the employment contract or general practice). Specifically, unliteral, fundamental changes to the terms of employment are generally illegal without employee agreement, and usually this in and of itself is insufficient without adequate compensation and/or notice.
If you have any questions relating to employment matters in the COVID-19 era, or if you have questions related to vacation, leaves of absence, lay-offs, terminations of employment or otherwise, please contact Toronto employment lawyers, Sultan Lawyers at 416-214-5111 or via email at firstname.lastname@example.org.