LINCOLN, Neb. (AP) — A commission that will decide whether to approve the Keystone XL in Nebraska is allowing the pipeline’s opponents to formally participate in its proceedings.

The Nebraska Public Service Commission’s chairman announced Friday that he will let groups such as the Bold Alliance, the Sierra Club and the Ponca Tribe of Nebraska become intervenors in the case. Intervenors are allowed to write legal briefs, cross-examine witnesses and present formal arguments alongside pipeline developer TransCanada’s attorneys.

Commission Chairman Tim Schram says the groups can only discuss issues outlined in state law. The tribes can only focus on the project’s social and cultural impact, and environmental groups can only make arguments about the project’s impact on soil, plant life and other natural resources.

Landowners along the proposed route were also granted intervenor status.