United were one of the driving forces behind the measures agreed on Thursday, whereby clubs will not be permitted to rack up losses of more than £105 million over three years.
Clubs 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.
However Ferguson sounded a note of caution.
"It's all good in theory, but the application of it will always be difficult," he said. "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 a problem to try to enforce it."
Under the measures, clubs whose total wage bill is more than £52m will only be allowed to increase their wages by £4m per season for the next three years, though that cap does not cover extra money coming in from increases in commercial or matchday income.
Arsenal have also pushed for financial fair play, but Gunners boss Arsene Wenger said he favoured more individual freedom for clubs.
He said: "I personally am for financial fair play in the way that companies and the clubs respect to manage the club with their own resources.
"For the rest I am for freedom, how you use your resources inside the club. I am not in favour of a Brussels-type of society with centralised control with complicated rules. I believe every company should live within its own resources. For the rest, leave it to the company to manage their company how they want to do it.
"It is nonsense because we live in a world where, if you look at Europe, most of the countries are in a very difficult financial position and I believe the minimum we can do in our world is respect the financial balance."
West Ham manager Sam Allardyce said he hoped the new regulations would not lead to the club losing their top players.
He said: "Like everything else it will probably start and we will have some flaws and if they get adjusted and amended as we go along that is fine. We will all have to try and live with what the new regulations will be when they are put in place. My only fear, from a personal point of view, is I hope we don't lose our best players."
- Sports & Recreation