The DOJ has reportedly contacted players’ agents about the PGA Tour’s bylaws concerning their ability to play in other golf competitions.

Those bylaws were part of an investigation in 1994 when the Federal Trade Commission found that the PGA Tour had violated antitrust laws, only to decide against taking any action.

The DOJ’s probe, first reported by the Wall Street Journal, comes one month after the PGA Tour agreed to suspend all its players taking part in the Saudi-backed series.

Major winners Phil Mickelson of the United States, Louis Oosthuizen of South Africa and Sergio Garcia of Spain are among 17 players who have been suspended by the PGA Tour.

"This was not unexpected" a representative from the PGA Tour told CNBC about the investigation.

"We went through this in 1994 and we are confident in a similar outcome."

PGA Tour commissioner Jay Monahan chairs the International Golf Federation Board.

The LIV Golf Invitational Series is particularly controversial because LIV Golf is majority-owned by Saudi Arabia's Public Investment Fund (PIF).

The PIF is Saudi Arabia's sovereign wealth fund and critics say the country is using it for sportswashing.

LIV Golf players have been cleared to play in the 150th Open Championship, scheduled to run from Thursday (July 14) to Sunday (July 17) in Scotland.

But their presence in the field continues to cause controversy, with 15-time major winner Tiger Woods of the US criticising LIV players for turning their back on those that helped elevate them to their lofty position in the sport.

"I just don’t see how that move is positive in the long term for a lot of these players, especially if the LIV organisation doesn’t get world ranking points and the major championships change their criteria for entering the events," said Woods.

"It would be sad to see some of these young kids never get a chance to experience it and experience what we’ve got a chance to experience and walk these hallowed grounds and play in these championships."

Greg Norman, chief executive of LIV Golf Investments, has been refused entry into events at St Andrews this week.

Norman triumphed in the 1986 and 1993 Opens but has been denied the chance to compete in the Celebration of Champions or attend the Champions’ Dinner.

Woods defended the Royal and Ancient Golf Club’s decision, accusing the Australian of not doing things in the "best interest of our game".

"I know Greg tried to do this back in the early '90s," said Woods.

"It didn’t work then and he’s trying to make it work now.

"I still don’t see how that’s in the best interests of the game.

"What the European Tour and what the PGA Tour stands for and what they’ve done, and also all the governing bodies of the game of golf and all the major championships, how they run it.

"I think they see it differently than what Greg sees it."