When the internal audit activity does not have the appropriate skills to review the organization's compliance with recently introduced legislation on international transfer pricing, the most appropriate course of action is to outsource the engagement to an external audit firm that has the necessary expertise. This ensures that the review is conducted thoroughly and accurately by professionals with specialized knowledge, maintaining the quality and reliability of the audit work while addressing the specific requirements of the engagement.
The IIA's International Standards for the Professional Practice of Internal Auditing (Standards) - Standard
1210: Proficiency.
The IIA's Practice Guide on Coordinating Internal and External Audit Activities.

According to IIA guidance, business ethics may indeed vary within an organization with both domestic and foreign operations. This variation is due to differing cultural norms, legal requirements, and business practices across countries, which may necessitate adaptations in ethical policies and practices. While the core principles of ethics might be universally upheld, their application can differ based on local contexts.
Institute of Internal Auditors (IIA) - Code of Ethics, International Professional Practices Framework (IPPF)

According to IIA standards, the internal audit activity should assist in maintaining effective controls but should not assume management's responsibilities, such as implementing or ensuring controls, to preserve its independence.

The best choice for a continuing professional development requirement for a newly created internal audit activity is to require all internal auditors to create a training plan based on a competency self-assessment. This approach ensures that training is aligned with the specific needs and gaps in skills identified by the auditors themselves, thereby promoting effectiveness and professional growth within the audit function.
IIA guidelines on continuing professional development and competency assessment.