Well MCC has rights to alter the laws of cricket.
I cant find out exact article which states that MCC scrapped it but if you see the following article from CRICINFO, it clearly talks abt bringing the same rule back!
So it indirectly means that the rule of allowing bowler to RUNOUT non-striker before delivery was scrapped at some point of time in the past and cricinfo wanted it back.
Cricinfo XI: Laws that need changing | Regulars | Cricinfo Magazine | ESPN Cricinfo
Disallow backing up
The running out of a non-striker was, for some odd reason, always deemed unsporting, but attempts by the batsman to steal ground on the fielding side are not?
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it is utterly inconsistent to allow the non-striker to gain an advantage of this magnitude."
When the MCC decided the non-striker could not be run out it inadvertently legitimised cheating.
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A bad law change not thought through. Reverse it and let the umpire decide if a batsman has genuinely been hard done by.
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Also if you think, why wud they say "new laws or change in laws", if that rule existed currently?? So as I said (and by memory) the rule was scrapped but now they have brought it back and hence termed as "law/rule changes"