Those conditions might only be fulfilled while the card or ability is on the chain. In such a case, it can still be played or activated at the appropriate timing as long as doing so could fulfill the conditions.
§ 813.4.a Core Rules PDF (officieel)
§ 813 Reaction
§ 813.4 Some passive abilities may grant a card or ability Reaction under certain conditions. The card or ability does not have the Reaction keyword unless and until those circumstances are true.
