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Sevendays DWI is a Capital Offense in Canada which is what a Felony means under US law, however in the USA a DWI is only considered a Misdemeanor charge.
When your friend tries to enter Canada with a DWI from the USA, his charge is appraised under Canadian law, not under US law and therefore he is not allowed into Canada as a result of his DWI being evaluated as a Capital Offense.
Just as a matter of interest, back in 2016 when Trump won his first term as POTUS, thousands of Americans flooded the Canadian Immigration website trying to become a Landed Immigrant in Canada. When the online application forms were then filed with Canadian Immigration authorities, 80% of all American applicants were denied because of this DWI infraction issue which disqualified them from even entering Canada, let alone living in Canada.
Driving while under the influence is considered not a big deal in the USA, whereas in Canada you'll have your car confiscated, your license will be suspended and you'll end up in jail for a month. And if it happens a second time to a Canadian, they will permanently lose their drivers license and go back to jail for 5 years.