French here
What's your friend describe is a "mise au placard". It's a specific way to fire somebody without really firring him.
It's extremely wrong in french for your managing staff motivations when you start to fire people without serious reasons and it's pretty hard to prove and convince every body that some body don't actually do as expected. So you don't fire him but progressively put him in a position where he don't have responsibility, interesting works, no computer, no phone, etc... and you simply wait that he resign by himself.
If he resign he isn't cover by the social protection law, so it's cheaper for you, better for you managing staff, etc...
The only problem is went you push it to far ( excessive work load, harassment, etc ) and the employ commit suicide ( Renaud technocenter serial suicide at work )
The "mise au placard" have nothing to do with this case where the employ was fired for "important fault". In this case the employer say "you committed an important fault in regard of the company, you are fired, you will not get the social protection".
Driving a truck drunk = important fault
sending a mail to his MP = ?