I will look up the law to be sure !
https://www.cnt.gouv.qc.ca/conges-et-absences/vacances/vacan...
It says you're supposed to be able to take your vacation uninterrupted. You might want to check with them.
Is this a matter of principle for you or were you planning to go to some remote are with no Internet? If the latter, you could just explain the situation to your boss and they will probably understand.
However here’s the reality: If your employer dislikes you, they can fire you for some false reason. You then take it to court and you win. You will be awarded some amount, and there’s now a legally defined cap on that amount, which the employer knows before they fire you. The amount is roughly one month’s salary for each year worked at the company. And you don’t get your job back.
Of course not all employers use this strategy for various reasons, but it exists as a possibility, so it has to be taken into account when planning what response is in your best interest.
But your username and grammar make me wonder whether you're French and in France, are you? If you are, I think it may actually be an illegal request. European attitudes towards work are extremely different to US ones, which are themselves more relaxed than e.g. East Asian.
From https://newatlas.com/right-to-disconnect-after-hours-work-em... :
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"France, in particular, has been ahead of the world in establishing legal frameworks protecting a person's right to disconnect. Back in 2001 the idea was first floated when the French Supreme Court ruled that employees are under no obligation to bring work home, and as technology progressed the Court continued to update its ruling. In 2004, for example, it was established that it was not misconduct if an employee was not reachable on a smartphone outside of work hours.
The right to disconnect was solidified at the beginning of 2017 with France introducing the El Khomri law, which suggests every employee contract must include a negotiation of obligations required of an employee regarding how connected they are outside of office hours. The law is reasonably vague and doesn't restrict after-hours work communication, but rather obliges organizations to negotiate these terms clearly with prospective employees."