Saw this situation over the weekend:

B1 reports to table for substitution as A1 brings ball up court. Official calls time-out to tell A1 to tie his shoe.

B1 wants to enter, but official says he cannot enter because it was an official's time-out.

I couldn't find a rule stating whether a player can enter the game in this situation.

Under FED rules, a substitute is allowed to enter after any dead ball, provided s/he properly reports, and it is before the expiration of a timeout. Inadverdant whistles, official timeouts, and other stoppages are all dead balls, and subs can enter. However, if this was a highly contested game, I would not stop the game for the player to tie the shoe, the team must call a timeout for this.

Matt is correct. I wouldn't stop the game for a player to tie a shoe. If we have a dead ball, I will wait to put the ball in play so a player can tie his shoe.