Fed rule
 

Can't find anything in rule book.
Bases loaded, no outs, all 3 runners are off their bases before pitch released. How many outs could you get?
If possible, mention rule #.

One.

You can only get one out when multiple runners leave early. 8-7-18

I see something under 8-6-18. But it doesn't say anything about only penalizing one runner?

The effect of 8-6-18 is that the ball is dead. One runner must have left before the other therefore only one is out. It's your job to decide which.

Thank you for your response, that's what I wanted to know!

The only organization I know where multiple runners may be ruled out for leaving their bases early is NCAA. That's because unlike any other sanction, an LBE violation is a delayed dead ball at the college level.

For those where there's an immediate dead ball ruling, in theory someone left first. The umpires then have to judge which one left first should more than one runner be in violation.

Manny:

I am going with the one closest to HP. Just my humble opinion; I have yet to discuss this play with Mark, Jr. but I would speculate that he would agree with me at least he had better agree with me. :D!

MTD, Sr.

This is not true.

This part is true. Then, the defensive team has the option of taking the penalty for leaving early or taking the result of the play. If the penalty for leaving early is taken, they get one out - whichever runner was judged to have left their base first. If the batter lines out into a DP, then the defense can take the result of the play. They get two outs, but not because two runners left early.

I believe the above to be true, but I no longer have an NCAA Rules Book to verify it and provide Rules references.

NCAA rules and interpretations here.

Like Manny, I don't know of another organization that treats leaving early as a delayed dead ball or allows more than one runner to be called out.
If you know of one, please let the board know.

In the NCAA case book:

A.R. 12-38.
With the bases loaded, the batter takes the pitch but the runners
on first and third base both leave early. Are both runners out?

RULING: The defensive coach may choose between taking the results
of the play (a ball or strike as called by the plate umpire, bases remain
loaded) or "no pitch", the batter remains at bat and the offending
runners are both declared out.
(Rule 12.14.2)

Thanks. Like I said, it has been a while since I last had the chance to look at it and that is a change from then. I think. :)

I'm fairly certain that even before the NCAA changed the LBE violation from an immediate No Pitch like it is in NFHS, USA Softball, etc., to a delayed dead ball, a case play existed where more than one runner could be ruled out. It was in a list of case plays that Dee Abrahamson, the Secretary Rules Editor from 1996 to 2016, had put out before they were officially codified in an NCAA Softball Case Book. If memory serves, it was when more than one runner left their bases simultaneously.