The Little League rule book lists something like 13 possibilities when a runner leaves early, depending upon the situation.
None of which call for a runner to be declared out by the umpire.
Life would be simpler if they adopted the softball rule of dead ball, no pitch and runner is out.

It IS simple. Runners can only go as far as pushed by the batter's clean (and safe) advance.

Any outs achieved during the play count.

So, I shouldn't have spoken up about Little Leage and being off base. I haven't work LL in years and was not familiar with the rule. I was commenting based on the OP's comment of the ump calling without the warning.

Unless the rules require a warning like NFHS removal of a helmet during a live ball, coaches and parents should expect one.

Not so simple when the rule list 13 possibilities.
One of which is to disallow a run and remove a runner from 3rd base.

The other 12 are just various example of runners only going as far as pushed by the batter's clean safe advance. There to answer a coach's "yeah but".

I will NOT officiate a league that has a "must slide rule" because of the above mentioned reasons.
The gentleman that got me into officiating changed our local softball & baseball league's slide rules. That was in the early 90's. We've on occasion had to remind a league board that there is a "sliding rule" in the books.

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