Here are some steps that could help resolve the conflict:
1. Have an open discussion where both parties explain their perspectives calmly and respectfully. The regional manager should understand the HR manager's expertise in recruitment.
2. Involve the central HR team to review the new decentralized hiring process and provide guidance on best practices. Getting input from HR experts could help address concerns.
3. Consider a hybrid approach where departments provide input but the HR manager oversees the actual recruitment and hiring in line with legal and process requirements. This shares responsibility in a balanced way.
4. Set clear guidelines for the roles of each party to avoid ambiguity and power struggles. Clarify that the HR manager is ultimately accountable for recruitment.