I was playing in a Tourney a few weeks ago, and my opponet tried to Stifle my Ali from Cairo. I said Ali has an inherant ability that can not be Stifled. He agreed and I was just trying to get further clarification. Thanks.
Hi
You use some confusing terminology which prevents from finding and applying the right rules, although the result of your answer and my clarification is the same. So you were on the right track

For the Oracle text of the cards:
Ali from Cairo: {2RR} |Creature -- Ali-from-Cairo| 0/1. Damage that would reduce your life total to less than 1 reduces it to 1 instead. AN-U2 (Oracle Version Date: February 1, 2004.
Stifle:

|Instant| Counter target activated or triggered ability. (Mana abilities can't be countered.) SCG-R (Oracle Version Date: February 1, 2004.
Ali has a static ability that results in a replacement effect (recognizable by the keyword 'instead') which replaces every single event that would put Ali's controllers life total to less then one by an event that puts Ali's controller life total to one.
Stifle only interacts with activated ability (recognizable by the phrase "activation cost: effect") or triggered ability (recognizable by the keywords at the beginning of a paragraph "When", "Whenever" or "At").
Additionally, if you play a Stifle, illegally targetting the Ali, you have to reverse that play, untapping mana sources and taking the Stifle back into your hand. You are not forced to replay the Stifle. At higher Rules Enforcement Levels (RELs) you'll receive an explanation and a warning for this misplay. At lower RELs you'll receive an explanation and a caution.
Jaap
[edit: corrected terminology]