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.

The Fundamentals of Risk Management in ISO 27001
URM’s blog explains the requirements of ISO 27001 Clause 8.1 and why it matters, as well as sharing key insights on how to properly implement it in practice.
URM’s blog explains the requirements of ISO 27001 Clause 8.1 and why it matters, as well as sharing key insights on how to properly implement it in practice.
URM’s blog explains how to meet ISO 27001 Clause 10.2, including finding nonconformities, performing root cause analysis, implementing corrective actions & more
URM’s blog breaks down ISO 27001 Clause 7.5 requirements, with practical guidance on how to achieve conformance to this Clause & what external assessors expect.

