A party to the contract may join in the arbitration as a party, any supplier, subcontractor, design professional, surety, or other person who has so agreed and if the joinder is necessary to prevent a substantial risk of the party otherwise being subjected to inconsistent obligations or decisions.
Source:
Section 10240.9, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=PCC§ionNum=10240.9..