Defensive verbal cues to the offense?
 

Is it legal for an infielder to yell "back" to a baserunner at second base in an attempt to distract him?

What rules?

FED, OBS.
NCAA and OBR, legal.

NFHS case play 2.22.1(A). Obstruction.

What does that say?

NFHS rules

2.22.1 SITUATION A: R1 attempts to steal second. F2, upon receiving the pitch, throws a pop-up to F6. F5 yells “get back, get back.” R1 thinks B2 has hit a popup and starts back to first where he is tagged out. RULING: This is verbal obstruction and R1 shall be awarded second base.

That seems entirely different from the OP, to me.

So the runner who is leading off 2nd base should be awarded 3rd base if the Shortstop yells "back" continually??

Not in my games. Now, maybe if F6 yells it, causes R2 to return just as the ball is hit, and R2 is out on a close play at third. But, who's going to see that?

The OP didn't describe the circumstances - only the yelling of "back" to distract the ruinner.

The first time he yells it, I will tell him to knock it off.

The second time, I'll stop the game and record a warning with PU and the head coach.

The third time, we'll need a sub.

Wrong!

If you are doing a FED game, it's obstruction - no questions asked (Rich Ives can correct me but I think in LL this holds also).

If you are doing NCAA or OBR, you have no grounds to do anything because there is no verbal obstruction rule as in FED. If you give a warning or stop the game, the coach can protest and you will be ruled against.

Nope. You're not getting it. It can't be obstruction unless it hinders the runner. I'm addressing it before that can happen.

Officially ther's no verbal obstruction in LL. Unofficially you treat it as UC in majors and below. (Fake tags are obs in LL)

It hindered the runner. He returned to 2B. Unless you are a mindreader, you don't know if there would have been an attempt to steal or not. The offense was deprived of that opportunity due to an illegal act by the defense.