http://www.usga.org/Rule-Books/Rules-of-Golf/Rule-06/
From USGA.org
6-6. Scoring In Stroke Play
a. Recording Scores
After each hole the marker should check the score with the competitor and record it. On completion of the round the marker must sign the score card and hand it to the competitor. If more than one marker records the scores, each must sign for the part for which he is responsible.
b. Signing and Returning Score Card
After completion of the round, the competitor should check his score for each hole and settle any doubtful points with the Committee. He must ensure that the marker or markers have signed the score card, sign the score card himself and return it to the Committee as soon as possible.
PENALTY FOR BREACH OF RULE 6-6b:
Disqualification.
c. Alteration of Score Card
No alteration may be made on a score card after the competitor has returned it to the Committee.
d. Wrong Score for Hole
The competitor is responsible for the correctness of the score recorded for each hole on his score card. If he returns a score for any hole lower than actually taken, he is disqualified. If he returns a score for any hole higher than actually taken, the score as returned stands.
Note 1: The Committee is responsible for the addition of scores and application of the handicap recorded on the score card – see Rule 33-5.
Note 2: In four-ball stroke play, see also Rules 31-3 and 31-7a.
The scorecard rule was quoted as 33-7 in the presser. And I’m not toally sure on jurisdiction, but Masters play may not be 100% consistent with USGA rules - which is the body that runs the US Open but not typically PGA events. I mean, there’s some commonality among all golf bodies, but not 100%. It was, apparently, a Masters Committee that ruled on it, so they may be Masters rules.
As for the scorecard rule in the first place, it’s outdated and no longer necessary.