A change order is valid when the project owner (client) and contractor sign it. But if the parties can’t agree, the owner may use a construction change directive (CCD) instead. A CCD is a unilateral instruction that doesn’t require consensus. According to the American Bar Association, contractors may not refuse to comply with the CCD — doing so is a breach of contract. However, that doesn’t mean contractors must yield to demands that fundamentally alter the contractor’s initial obligation. The cardinal change doctrine protects contractors from agreeing to build a church and then being forced to build a hotel instead, for example.