[teebob21]

ASA covers this well in RS #36. The obstructed runner would be called out on the completed live-ball appeal for leaving the base before the fly ball was touched, if in the umpire's judgment the runner would not have been safe absent the obstruction.

If the runner reaches the base they would have been awarded (returned to 1B in this case), the obstruction is cancelled and the runner may be put out anywhere on the base paths if they advance.

The mechanic IMHO would be to signal the DDB per ASA 8-5-B, then make the call based on what happens after the OBS. But if a snowball fight breaks out, don't run around out there with your left arm out. Signal and vocalize, hold, and move on.

In NCAA, my understanding is that the runner who needs to tag up is not protected between the two bases by rule if advancing, per 9.4.3.5 and its Approved Ruling. However, 9.4.3.2 indicates that a runner obstructed while returning can be protected if the "obstruction causes the out"/would have reached safely absent the OBS. There was another thread on the board earlier this year on that topic.

In NFHS, the rule matches my NCAA interp, i.e, runner not protected when advancing; is protected if she is returning, per 8.4.3b.a(2). <--- Not a typo, that's actually how the sections are labeled, at least in my 2015 book.