Law believes that Fergie's support behind the scenes will prove vital - with his successor able to call on him for advice.
He told the Manchester Evening News: "It's always a problem when someone new comes into a job.
"They've got to get to know the staff, the players, how things operate. Things take a little bit of sorting out, it doesn't come straight away.
"When Sir Alex joined United, things weren't too good there but the board were fantastic with him and they reaped the rewards.
"If you're the type of man like David Moyes is, there won't be any problems.
"He's such a nice man, a good manager and it's early days. If Sir Alex picked the guy, that's good enough for me. He's a difficult man to take over from. It was the same with Sir Matt Busby when he decided to retire.
"Sir Alex won't get involved but if David wanted some advice, he'll be there for him, guaranteed."
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