The 37-year-old from the city of Reims registered with the interior ministry last year to be voluntarily banned from casinos and online gambling sites, but was still able to access them, lawyer Emmanuel Ludot told AFP.
"It's all well and good to moralise about online games but we all know that they rely on the addiction and sickness of players," Ludot said.
He said the ministry registered the man, whose identity was not released, under the wrong address when he asked to be banned, "which allowed him to continue playing".
The interior ministry refused to comment on the case because legal proceedings were under way.
Under French law gambling addicts can register with the ministry to be banned from casinos and from being allowed access to Internet gambling sites, which must consult the ban list before allowing players to sign up.
There are currently about 36,000 people registered on the list.