Here is a video (with sound) of the card counter in the "back room", being pressured by Maryland cops to give his ID to the casino, under threat of taking him to the police station and force-IDing him through fingerprints if he refuses:
Here is a short, no-sound video of the same card counter being forcefully backroomed:
The cops are full of shit. Nowhere in the US (including Maryland) is it required that you have ID while at a casino. The casino does have a right to kick you out for any reason (including failing to show ID), but they cannot force you to present ID, nor can the police do it on their behalf.
The only exception is if the police are placing you under arrest and need to identify you, but in this case they were not arresting him or charging him with anything, as he hadn't done anything illegal.
In case some of you are wondering why he didn't just show ID and be done with it, be aware that casinos share information on card counters, so you really don't want your name in the system that way.
I was once asked to show ID after being caught counting in a Vegas casino. They asked why I wouldn't show them my ID, and I answered, "Because it's my right not to." To their credit, they accepted that answer, though they did ban me from the property. It is possible to ban someone without having their name, simply doing it by picture.
The casino is also NOT supposed to forcefully backroom customers unless they are suspected of cheating, and card counting does not fall under the "cheating" heading here.
I hope this guy sues the casino and the police for this and wins a lot from them.