What is this Geis from? On the Type-Moon Wikia entry for Geis it says this:


  Contract used by Kiritsugu Emiya 
  Binding magecraft: Target – Kiritsugu Emiya 
  The Crests of the Emiya family hereby command: Provided that the following conditions are met, this oath shall become a commandment and bind the target without exception. 
   
  Oath: 
  To the fifth head of the Emiya house, Kiritsugu, son of Noritaka: regarding both Kayneth Archibald El-Melloi and Sola-Ui Nuada-Re Sophia-Ri, all intentions and actions to kill and harm shall be forbidden for all eternity. 
   
  Conditions: 
  Use up all the Command Seals, and let the Servant finish himself.


Now I've only seen up to Episode 10 but from how this reads it seems to have been in place before even the first fight between Saber and Lancer since by episode 10


   Sola-Ui Nuada-Re Sophia-Ri is Lancer's Master and probably doesn't care about Kayneth since she loves Lancer


However, Kiritsugu had tried to kill Kayneth on more than one occasion and there seems to be nothing that tries to stop him from breaking this Geis. in Fate/Stay Night in one of Heaven's Feel's bad endings, it's shown what happens when Shirou goes against the Geis he forms with Rin


   Once he plans on going against Rin's wishes of killing Sakura Matou, he finds that he cannot move his body at all to stop her. He is immediately freed upon Sakura's death, as there is no longer any reason to bind him.


and in Cú Chulainn's legend, his demise was caused when he was put in a situation where he had to break a Geis


Never refuse a meal offered by a woman
Never eat dog meat


He was offered a meal of dog meat by a woman and as such he had to break one Geis.

So while I may be jumping the gun here and asking this before watching the entire series, where does this Geis with Kiritsugu and Kayneth appear? If it was before the first fight between Saber and Lancer, how come there was nothing enforcing the Geis as there was with Shirou?
Spoilers for the second half of Fate/Zero:


   After the defeat of Caster in episode 15, Kayneth goes to the church (in episode 16) and asks Kirei's dad for a Command Spell as a reward for having helped defeat Caster (not that he did a damn thing; that was all Lancer). Kirei's dad agrees and gives him a Command Spell. At more or less the same time, Maiya abducts Sola-Ui and also cuts off her arm with the Command Spells. Lancer returns to Kayneth at this point, no longer able to locate Sola-Ui now that her Command Spells have been severed.

 Saber (with Irisviel) happens upon Lancer at this point and they start dueling. Meanwhile, a bit away from the duel, Kiritsugu shows up with Sola-Ui's body and proposes a geis to Kayneth - Kiritsugu will leave Sola-Ui with Kayneth and shall nevermore harm either of them, provided that Kayneth uses up all his Command Spells and orders Lancer to commit suicide. Kayneth agrees, since that appears to be the only way out of the situation, and compels Lancer to kill himself. Kayneth breathes a sigh of relief, since he and Sola-Ui are now safe from Kiritsugu and Saber.

 Of course, Maiya is lying in wait with a sniper rifle, and kills Kayneth and Sola-Ui immediately thereafter. She wasn't bound by the geis, after all. Sucks to be Kayneth.

 In any case, only a few minutes at most pass between the geis taking effect and Kayneth/Sola-Ui being assassinated by Maiya (which renders the geis moot). The geis emphatically was not in effect at any time before that, and as such did not impact Kiritsugu/Saber's previous fights with Kayneth/Lancer.