SimCity modders cannot sell their content, affect multiplayer features or modify executable files when creating new content, Maxis announced via the game's website.
According to the post, guidelines are in place to maintain the "safety and integrity" of the game while still being clear about modder rights.
"EA reserves the right, in its sole discretion, to revoke permission to use, distribute or make mods at any time, to disable any mod within SimCity and to take disciplinary action against players who harm the experience of others," the post reads.
Mods that "affect the simulation for multiplayer games or multiplayer features," infringe on other properties or break any rules listed on the website will be removed.
"We encourage you to create, redistribute, and consume mods for SimCity, as long as you respect all of the rules and guidelines set in this policy," the post reads. "By mods we mean any modifications or alterations to SimCity, including add-ons, new content, modified UI, or updates that use content from SimCity such as code, art, footage or other elements (the 'SimCity Content')."
The always-online title launched in March 2013 with a plethora of server and connection problems. After numerous patches, the game was finally restored to stable status. For more on SimCity, read our review.