What rule prevents a card from being played if its effect is known to be unresolvable?

Question

The Pokemon TCG Rulings Compendium contains multiple rulings that imply that cards cannot be played if it is known their actions cannot be resolved.

For example:

Can I play Accompanying Flute if my opponent's Bench is full? - No

Can I use Professor Elm's Training Method if there are zero cards left in my deck? - No, you cannot search through your deck if there's nothing there to search.

Could I [...] search through my deck for a particular card if I already know that card is not in my deck? - Yes , you may.

These and other rulings imply that you cannot play a card to fail it if it is known that the action is unresolvable. Most players also know this to be true and play accordingly - The official rulebook, however, does not explicitly state this to be a rule and I cannot find a ruling that applies this logic to all cards.

While the rule can be inferred from past rulings to apply across all cards, is this rule stated explicitly in general terms in any official Pokemon TCG resources?

Answer 1

Ultimately, this is based on a rules team question from early days, now found in the compendium:

You cannot play a card if it is public knowledge that it will have no game effect. Paying a cost does not satisfy the requirement that the card has a game effect.

This does go somewhat further back, for what it's worth - for example, from 2004:

Q. Magneton's "Magnetic Field" Poké-POWER states: "Once during your turn (before your attack), if you have basic energy cards in your discard pile, you may discard any 1 card from your hand. Then search for up to 2 basic Energy cards from your discard pile, show them to your opponent, and put them into your hand." Can you discard the energy and choose none because it states "search for UP TO 2 cards"?

A. You cannot play a card to no effect when failure of the effect is known in advance. In this case, since you know there is energy in the discard, you must take at least 1 to play the card. (Mar 18, 2004 PUI Rules Team; September 18, 2007)

There is no "better" source than that; as you note the rulebook does not specify this. For better or for worse, Pokémon has chosen to have a very simple rulebook that does not remotely contain all of the detail needed for proper competitive play, and to put that into the apocrypha that is the Compendium.