Clubs will not be permitted to rack up losses of more than £105million over three years.
They will also face limits on the amount by which they can increase their total player wage bills - and breaching either measure could lead to points deductions.
Ferguson said however: "It's all good in theory but the application of it will always be difficult. If people have money to burn they can place it anywhere in the world.
"I'll be interested to see how they think they can operate it. It would be good if it was applicable but I have my doubts. I think it's always going to be problem to try to enforce it."