There's no other option but treatment. 'Locking [him] up' is an inhumane (and, as I'd expect you to know, impracticable) response, as is leaving him to his own devices.
The only solution is to put him in a place where he can't drink, can't interact with the outside world and can reflect upon what a thorough mess he's become and why.
He needs to be imprisoned or detained under the MHA for a long period, not days, weeks or months.
He's fucking ill you arsehole!
Soz pal. Forgot being detained under the MHA was only for those who are a bit silly.