Originally Posted by jrmonty
#1 is actually correct at showdown they can force you to show your cards although it is against etiquette.
NO this isn't quite what the OP was talking about.
At showdown the person who bet last has to show his cards first.
Then the caller can either show a better hand or fold.
In the OP's description the table thought the caller should show first.
After the better has shown and the caller mucked... then a player may request to see a player's mucked cards.
This rule exists to prevent colluding, i.e. the mucked hand beats the winning hand, but is mucked anyway.
Whilst any player is free to ask for this at any time, its frowned upon because it gives away information for free and as the rule is there to prevent cheating, you are basically accusing the guy of cheating by invoking it.
There is no official limit to who how or when it can be used, but some casinos
will issue a player with a warning if they feel he is asking to see mucked cards too often.