This section requires expansion
After learning of a planned attack on Earth by the Goa'uld System Lords, the Asgard Thor comes to Earth in his ship and informs Colonel Jack O'Neill about the threat and offers Asgard help. As the Asgard fleet is engaged elsewhere, Thor offers to protect Earth by negotiating with the System Lords to include it in the Asgard's Protected Planets Treaty. Though O'Neill prefers the Asgard using their ships to defend the Earth, as that isn't an option, he agrees. Soon afterwards, Thor notifies SG-1 and Major General George S. Hammond that the System Lords have agreed to negotiate and are sending three representatives by Stargate in four days for the summit. Along with information on the three Goa'uld, Cronus, Yu and Nirrti, Thor sends orders that all weapons be removed from the base as no weapons are allowed during the summit from either side. Reluctantly, especially in Teal'c's case, they comply with this order and remove all weapons from the base and seal it off. Secretary of Defense Arthur Simms remains on the base to represent the President of the United States while the Asgard choose a reluctant O'Neill to act as Earth's representative as he led humanity into the stars through the Stargate despite his preference that Dr. Daniel Jackson, who is assigned to act as the Goa'uld liaison, be the representative.
Four days after Earth is notified, the Goa'uld arrive and are assigned VIP quarters which they are unhappy with. After being shown to their rooms, tensions rise when Teal'c and Cronus see each other and when Nirrti and Yu discover surveillance cameras in their rooms which they demand removed. Jackson is able to calm the situation and comes up with the compromise that the cameras will be removed from the rooms but remain in the halls which the Goa'uld agree to. Cronus also demands Teal'c stay away from him and Teal'c explains to Jackson that he hates Cronus deeply as Cronus murdered his father after he lost an unwinnable battle as Cronus' First Prime and has since sworn to get revenge. Soon after, as they wait for the negotiations to commence, Major Samantha Carter admits that she's realized that Cronus is the one that sent the Ashrak Edrekh tho kill Jolinar of Malkshur, the Tok'ra she was briefly host to and the attack she nearly died as a result of. The negotiations get off to a bad start as after Thor opens them, the System Lords start to insult each other in the Goa'uld language and O'Neill unintentionally insults them by speaking out of turn to ask if they could all speak the same language, causing the Goa'uld to storm out. Thor explains to O'Neill what happened and why the Asgard allowed the Goa'uld to get so powerful: they have a much worse enemy in their home galaxy and cannot spare the resources to fight the Goa'uld too. The Asgard rely on the System Lords to enforce the treaty out of fear of Asgard retaliation with the System Lords keeping even rogue Goa'uld like Sokar from breaking it. However, as the Asgard rely on this and Goa'uld's feudal nature, if a single Goa'uld rose to dominate power such as Sokar, the Asgard wouldn't have the power to stop them from attacking and enforce the treaty as they are pretty much bluffing the Goa'uld into thinking they have the power to stop them. Thor then gives O'Neill a way to contact him when the Goa'uld are ready to return to negotiations and leaves but not before warning O'Neill and Jackson that the negotiations won't be easy and both the Tau'ri and the Asgard will be required to make great sacrifices to succeed.
After Jackson types up an apology letter in Goa'uld and O'Neill signs it, the System Lords agree to continue and the negotiations resume. Thor agrees to open the Passage of Nilor to the Goa'uld in return for Earth's inclusion into the treaty, but the Goa'uld are reluctant as the treaty states that no human civilization protected by the treaty can rise to become a threat to the Goa'uld. They agree however, but demand the forfeiture of both of Earth's Stargates in order to limit Earth's development and eliminate the threat that humanity poses to them. The negotiations recess as the Tau'ri try to decide what to do as if they don't give up the Stargates the Goa'uld will destroy Earth, but if they do, there are other threats that the treaty doesn't protect them from and giving up Stargate travel would leave them vulnerable if the Goa'uld ever called the Asgard bluff and attacked anyway and they had no new advanced technology to defend themselves with. After O'Neill is unable to get an opinion from Thor about what they should choose, the President decides to agree to the Goa'uld terms, but before they can inform the System Lords, Cronus and Teal'c are found unconscious in Cronus' room. While Teal'c took a bad blow to the head, his symbiote will be able to repair the damage over time, but Cronus took severe internal injuries to the point where neither Dr. Janet Fraiser nor his symbiote can save him. The security camera tape of the incident shows Teal'c going to Cronus' room, but as there are no cameras inside Cronus' room, it looks like Teal'c attacked him in revenge for his father's death and they can't prove otherwise though SG-1 and Hammond believe him to be innocent. SG-1 inform Nirrti and Yu of Cronus' attack but not of Teal'c's apparent involvement and have Nirrti use a Goa'uld healing device to try to save Cronus. It doesn't work and Nirrti tells them that Cronus' injuries are too severe and he needs a sarcophagus to survive. As Earth doesn't have one, the Goa'uld prepare to leave to save Cronus and prepare their attack on Earth in revenge.
As the summit is apparently over, Thor is ordered to leave Earth and informs O'Neill of this fact, telling him that to stay and fight would put the Asgard into a greater war that they couldn't win at the moment. He also warns O'Neill not to imprison the Goa'uld as the other System Lords would attack anyway even if they didn't return to order the attack. Despite this, the Tau'ri imprison the Goa'uld and bring in soldiers armed with guns despite the rule that states no weapons are allowed. As they wonder how to prepare for the impending devastating attack, they receive word that Teal'c has regained consciousness. Teal'c explains his side of the story: he received a message from Cronus to meet him alone, but when he did, Cronus denied sending the message and they were attacked by an invisible force. When everyone assumes it might be a Reetou, Teal'c informs them that he didn't sense one and that he knows of no Goa'uld with invisibility technology besides Hathor who is now dead. Carter decides to try to use the healing device on Cronus herself and manages to heal his injuries, saving his life. In return for SG-1 exposing which Goa'uld attacked him, Cronus agrees to support the treaty without Earth having to give up the Stargate.
Realizing Nirrti lied about not being able to heal Cronus, O'Neill suggests bluffing that they know more than they do and confront Nirrti and get her to confess. O'Neill confronts Nirrti about failing to heal Cronus and claims that they talked to the Tok'ra who told them that Nirrti was experimenting with phase shifting technology to fight the Reetou. Nirrti denies it, but an enraged Yu attacks her, saying that she always coveted Cronus' territory and that she was the one that always opposed the treaty. When Yu strangles her, Nirrti turns invisible, grabs a guard's gun and fires at Yu who O'Neill shoves to safety. Nirrti tries to escape but when Carter corners her with a Transphase Eradication Rod which makes her visible and threatens to shoot, Nirrti surrenders. In the aftermath, Yu agrees to the treaty without Earth having to give up the Stargate and the attack on Earth is averted. The System Lords leave with Nirrti as Cronus' prisoner, but before he leaves he warns that while Earth will not be attacked, any Tau'ri found by the System Lords off-world will be shown no mercy. (SG1: "Fair Game")
The Protected Planets Treaty ends up protecting Earth for five years from Goa'uld attacks until Anubis rises to power at which time Earth eventually comes under attack from him in March 2004 but the Tau'ri find a way to stop it on their own. (SG1: "Lost City, Part 2")