Does he have to pay Canadian income tax on his world wide income?
Nope,
ONLY the United States and Eritrea impose taxes on their citizens living abroad. So dual national (say US/Canadian citizens living in Canada) have to file a US tax return every year. Failing to do so can incur significant penalties.
I had a gf who was born in Canada to an American mother who lived here all her life and Canadan father. She got a US passport for shits and giggles. A few years back, she got detained at UC Immigration for failing to use her US passport to enter the US AND also for failing to file US income tax returns. She had to hire a US lawyer. a Canadian lawyer and an accountant to sort out and file her US 1040's. Cost her $15k in professioonal fees.
How much tax did she owe Uncle Sam? Nothing. Zip, zilch, nada!
This is because she always filed and paid her Canadian tax obligations, which through a foreign tax credit, offset her US taxes.
The rest of the world taxes based on residency, where you are living and working. Well except for Eritrea who imposes a special 2% tax on all Eritreans abroad - dual-nationals included - in order to fund the dictatorial one-party government which has ruled since independence in 1993.