If they're the law, what's the point of the guild pact?

What happens to normal people who don't wanna be offered up as a sacrifice for rakdos? How can the authorities NOT cross the boundaries of the guildpact to stop that sort of thing. 

What is the city function of a barbarian guild?

The Guildpact only maintains the balance between the guilds, it doesn't enforce Ravnican law. The Guildpact prevents any one guild from rising up and taking over the plane; originally through subtle, magical means. For example, if a certain guild started growing in power, an opposing guild would suddenly come into just the right artefact to stop them. Or maybe the upstart guild would start experiencing unexplained failures in their plans. With the advent of the Living Guildpact, that intervention became more direct.

Normal people who don't want to be sacrificed to Rakdos generally don't, because the Rakdos Cult is a hedonistic pleasure cult and generally people give themselves willingly. If people were being kidnapped, the Boros Legions or Azorious lawmages would investigate and prosecute under Ravnican law; the Guildpact wouldn't prevent that as the Guildpact doesn't prevent guilds from interacting with each other.

The Gruul Clans don't have a direct function, they just exist. Tens of thousands of years ago, they represented a natural force of renewal, grinding down the city so nature could reclaim it and be refreshed. They worshipped the old gods of Ravnica, the ones that dwelled in the once ample forests and glades and valleys. The current clans are remnants of that, still hanging onto their role in the balance of things, but not really knowing why. Again, if they start destroying stuff, Azorius will intervene, but the Gruul will likely ignore them and go destroy something else. Once again, the Guildpact wouldn't stop this interaction, just ensure that it doesn't lead to the Azorious guild becoming dominant.

Also, fun fact, murder is not technically illegal in Ravnica as long as it doesn't disrupt Guildpact business. 

The Azorius and Boros work semi-collaboratively towards the enforcement of the law, with the Azorious filling more of a role of the Feds or white collar crime fighters and law makers in the areas of the city they control. The Boros on the other hand are more soldiers/beat cops/detectives and are less bound by the letter of the law and more it's spirit, and are more often prone to bouts of vigilantism. 

Quote from Davedamon >>

The Guildpact only maintains the balance between the guilds, it doesn't enforce Ravnican law. The Guildpact prevents any one guild from rising up and taking over the plane; originally through subtle, magical means. For example, if a certain guild started growing in power, an opposing guild would suddenly come into just the right artefact to stop them. Or maybe the upstart guild would start experiencing unexplained failures in their plans. With the advent of the Living Guildpact, that intervention became more direct.

Normal people who don't want to be sacrificed to Rakdos generally don't, because the Rakdos Cult is a hedonistic pleasure cult and generally people give themselves willingly. If people were being kidnapped, the Boros Legions or Azorious lawmages would investigate and prosecute under Ravnican law; the Guildpact wouldn't prevent that as the Guildpact doesn't prevent guilds from interacting with each other.

The Gruul Clans don't have a direct function, they just exist. Tens of thousands of years ago, they represented a natural force of renewal, grinding down the city so nature could reclaim it and be refreshed. They worshipped the old gods of Ravnica, the ones that dwelled in the once ample forests and glades and valleys. The current clans are remnants of that, still hanging onto their role in the balance of things, but not really knowing why. Again, if they start destroying stuff, Azorius will intervene, but the Gruul will likely ignore them and go destroy something else. Once again, the Guildpact wouldn't stop this interaction, just ensure that it doesn't lead to the Azorious guild becoming dominant.

 This answer works for me. It lets me think that the other cruel guilds have to abide by Azor law. And they have other legal businesses to attend to.