There is, generally, no direct legal requirement as such. Organisations choose whether or not to implement the requirements of ISO 27001 based upon the benefits that would be gained by doing so.
However, you should pay close attention to any contractual obligations you may have for protecting the information of clients and other stakeholders.
There is an increasing trend where customers require third party suppliers to implement or certify to ISO 27001, thus making it a legal requirement, by way of a contract.

ISO 27001 Clause 5.1: Leadership and Commitment Explained
URM’s blog explores Clause 5.1 of ISO 27001, what you must do to meet its requirements, and why leadership & commitment are vital to an effective ISMS.

URM’s blog examines how ransomware occur, and highlights practical cyber security measures you can implement to reduce your exposure and mitigate security risk.

URM’s blog breaks down the ISO 27001 certification process, the roles of certification bodies and UKAS, what auditors look for during assessments, and more.

URM’s blog explores the ISO 27001 business continuity controls, why they matter, & how they can be effectively implemented to ensure conformance to the Standard