Al Jazeera's Neave Barker, reporting from Moscow, said the government would also struggle to recuperate the $2bn generated by the industry each year.
"While the law aims to control crime and protect the vulnerable from poverty, it leaves those who rely on the industry with an uncertain future," he said.
Industry experts have also warned that the law could push gambling underground, with some businesses trying to skirt the law by rebranding themselves as poker clubs, under a quirk of Russian law that recognises poker as a sport rather than a game of chance.
The gambling law is expected to have the biggest impact on Moscow, which had 524 casinos and 35,000 slot machines until the law took effect, and in the northern city of St Petersburg, which had 109.
Russian news agencies reported that Moscow police were checking gambling halls across the capital on Wednesday to make sure they were closing.
Under the new restrictions, casinos and slot machines will be allowed to operate only in Kaliningrad on the Baltic Sea; the Primorsky region on the Pacific coast; the mountainous Altai region in Siberia; and near the southern cities of Krasnodar and Rostov, host to the 2014 Sochi Olympics.
But our correspondent says the plan is in disarray, with the site in Kaliningrad still an empty field, and few locations lacking any basic infrastructure.