The Rangers midfielder has been accused of breaching the SFA disciplinary code by staking money on 160 football matches - including bets made against the side he was registered with - dating back to 2006.
The former Hearts and Inverness battler now faces a potential £1million fine or a life-time ban from the game.
But Jack Ross, PFA Scotland's communications director, says Hampden chiefs should look again at the wording of their rules on the subject.
Black has been charged with breaching SFA Disciplinary Rule 22, which prohibits players from betting "in any way on a football match" - no matter where it takes place.
That is a stricter interpretation than is followed in England and Ross claims it makes little sense to punish players for betting on games that take place thousands of miles away.
"Should a player in Scotland's Second Division be banned from betting on a Champions League game?" he asked. "It's a good question and one that should be looked at.
"It comes from FIFA who want to protect their big international tournaments like the World Cup. It is they who say they don't want any betting on football but they don't take too much to do with how it is governed locally.
"In England it is competition-specific but the SFA have taken the decision to take a zero-tolerance approach to the whole issue of gambling on football.
"I suppose that begs the question about whether or not it should be enforceable or not and whether it is reasonable to deal with the issue in this way."
The PFA have set up a gambling awareness programme in conjunction with addiction counselling service the RCA Trust.
Union reps such as Ross have visited most of Scotland's 42 clubs to spell out what help is available to players who find themselves struggling with gambling although they do not tell players how to behave.
Ross explained: "We don't preach to the players and tell them what to do. We just explain what the rules are and what options are available to them if they are having issues with gambling.
"It's hard to quantify how serious an issue it is but I suppose the fact that we offer a gambling awareness programme shows that it is something that is required.
"As for players betting against their own side, it's not something that I have been made aware of either as a player or in my time working with the union.
"But it comes down to morality and in this country there is still a sense of fair play that makes that sort of thing very rare."
The SFA have stressed that there is no evidence that Black has breached rule 23, which relates to match fixing.
Ross could not comment on Black directly other than to say the 28-year-old had been offered support by the union but did stress that breaching football's betting rules and match fixing should not be confused.
"They are two very different things and the distinction has to be made," he said. "Match fixing can be connected to a number of sinister things and has lots of different causes.
"But simply putting a bet on does not mean you are guilty of that."