The Project Management Professional (PMP) emphasizes the importance of proactive planning and risk management. In this scenario, the project manager has identified a potential risk that could impact the project's execution. The best course of action is to mitigate this risk proactively by scheduling training for the key workers. This will ensure that they remain compliant with the new legislation requirements and can continue their tasks without disruption. References: PMBOK Guide, Risk Management, Proactive Planning. Please refer to the specific sections in the PMBOK Guide and PMP study materials for more detailed information.