How are Canadian police selected? Is there any hope of studying abroad as a policeman?

To apply for the Canadian police, your basic requirements are Canadian immigrants (legal permanent residents) or citizens.

In other words, it is absolutely impossible to obtain immigration status through the job of "police"!

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http://www.torontopolice.on.ca/careers/minreq.php

To be a policeman in Toronto, you must be a permanent resident or an immigrant. Only need to graduate from high school (grade 12). /kloc-over 0/8 years old, with vision of at least 20/40 (uncorrected) and non-color blindness. No criminal record, driver's license. Hold a C-level first aid/CPR first aid certificate before employment.

As far as I know, the above are only "minimum requirements" (few people are admitted according to the minimum requirements), so people who are usually selected have other professional licenses (such as social workers).