Drugs everywhere.
drugs that make people addicted to meat. eazy peazy
Add those drugs everywhere, cigarettes, cultivations,farms, forests... Maybe build machines that release this drug as gas on public zones 24h/7d.
anyway, executions are incredibly expensive three times as much than keeping someone in jail for from birth to death. your countryworld would go to famine and eventually fall with all the money spent on killing vegetarians or vegans.
To avoid an istanteous economy fall, the drug has to automatically kill people if they don't eat meat for more than 3 days cause even when drugged people with a strong morality won't sell their souls, specially empaths which are almost always only vegans or vegetarian people.
Anyway, great part of the human population will die anyway cause they don't eat meat for health reasons and forcing them to do so would be exactly like telling them to suicide.
Then another great part of humanity will die too for not being able to afford buying meat..... you'd expect to have a world with only 2-3 billion people instead of 7 billions
But anyway, meat consumation is so destructive that the economy will be destroyed anyway sooner or later.