Similarly one may ask, do employers have to pay you for your two week notice?
Generally, companies will honor the two-week notice and pay the employee for the last two weeks even if the employer does not allow the employee to work during that time period. However, there is no federal law which requires the employer to pay employees or even allow them to work during that two-week notice period.
Subsequently, question is, can you change your mind after putting in two weeks notice? Answer for the U.S.—it's the company's decision whether to allow you to change your mind. Because of mutual at-will employment, the company was required to accept your resignation. The employment relationship was severed at that point. It is the company's decision whether to allow you to rejoin, however.
Similarly, can an employer fire me after I give notice?
In most cases, an employer can fire you and stop paying you immediately after you give notice. That's because most employees are considered employed at will, which means that the company can terminate you at any time for no reason (with a few exceptions).
Do you legally have to give 2 weeks notice in Canada?
Unless there's an employment contract in force that states the amount of notice to be provided, Canadian common law requires that "reasonable notice" be offered by the employee when they resign. It's normal (but not a legal requirement) to give two weeks of notice. It's wise to also submit your resignation in writing.