I was watching NCAA-W game on Saturday. One team called a TO. I don't remember which team. Near the end of the TO, while both teams were still huddled, a player was at the table, having checked in to sub. At the end of the TO, one official told the player that they couldn't come into the game. They had to wait for the next dead ball. Anyone familiar with this? If it was interpreted wrong or even if the official was right, it doesn't make sense.

Are you saying that the sub checked in with the table before the first horn? If the sub checked in after the first horn then the sub must wait until the next opportunity to sub.

If the sub checked in before the first forn then the official probably made a mistake and thought the sub checked in after the first horn.

The rule states that all subs must report to the scorer prior to the first horn during a time out. I don't know how long this rule has been around but I'm pretty sure it's been in place as long as I've been officiating (15 years). It's difficult enough sometimes getting the players back on the court after a timeout. But add new subs reporting to the table to the mix and you would have an extremely disorganized and unstable situation.

However, I would be interested to know when the rule was implemented and if there were other reasons for the rule...if anyone knows.

If she reports after the first horn, she can't enter until the next opportunity to sub.

I honestly can't tell you when she checked in relative to the horn, but there were at least 30 seconds from the time she got to the table until the ball was inbounded. Both teams were still in their huddles when she reported and they slowly broke the huddle, returned their chairs to the sideline and then got ready for a throw-in.. It seemed silly to make someone wait because it happens all the time that a sub will run up to the table to report while the ball is just about to be handed to someone for a throw-in (after a violation or foul) or they run up to the table just before the second FT is made and they are allowed to enter. Quite possibly the rule was administered correctly, but even so, it seems silly to make someone wait for the next dead ball.

Actually had this happen the other day
a team comming out of a time out had sent a sub to the table to be put in after the first horn had sounded the scorer motioned the player into the game
The R was near the table and he pulled the player back out to the table to await the next oportunity - Two reasons
One the checking was after the horn -
Two the sub had just come out of the game during the time out and needed to wait until the clock actually ran before they reentered.
Something you have to watchout for.