When federal financial regulators last week adopted the massive Volcker Rule, it didn’t mean their work was finished. If anything, lawyers say the work is just beginning.

Legal challenges to the rule that bars banks from making risky bets with their customers’ money are a “virtual certainty,” said David Hooper, a corporate partner at Barnes & Thornburg. “The implications [for] banks are so widespread that it is highly likely there will be challenges to the final rule on a number of grounds.”