It can be, where the knowledge concerns the company's own validated methods and documentation rather than the published standards those methods implement.
Separate the public standard from the company's implementation of it
Sterilisation and validation practice rests on published international standards that any qualified specialist can read. Knowing those standards is professional competence and is available in the labour market. What can be special to the organisation is how this company applies them: its cycle development method, the parameters it has qualified across its own equipment, the bioburden and dose-audit protocols it has written, the rationale recorded in its validation files, and the customer-specific qualification packages it maintains.
That body of knowledge exists only inside the company and is learned there. Build the petition around that distinction explicitly, quoting from the company's own documents where possible. A petition that simply asserts deep expertise in sterilisation validation describes an industry skill set and invites the conclusion that the role could be filled from the American market.