Is getting jailed for being drunk legal?

I recently heard the story, from a friend of mine, that his friend was found outside an Abu Dhabi bar by policemen, drunk, and was taken into custody. Granted, the drunk guy had fallen (or passed out), so he was found laying on the street. He was first taken to hospital to get his alcohol level checked, and was then taken to jail where he's still being kept to this day.

He's been there for 5 days now and does not know when he will get out. The police moved him from one prison to another then back to the first prison, then again to the 2nd prison.

Is this legal? I mean, the guy was not driving, and as far as I'm concerned, if there are clubs/bars in the UAE, it means that you are allowed to drink. The guy did not get into a fight and he did not hurt anyone. He is Christian, southeast Asian, but does not have a liquor license. I understand that the police would jail someone for a day or two, but 5 days??

Can anyone shed some light on what the law says about this?