Continued Business Justification means that there is a purpose for continuing the project. This must include clear requirements, and clear benefits to the client/customer. There must also be a defined audience and cost assessment.
The project Business Case is the way that Continued Business Justification is monitored. Each Project Board meeting should review the Business Case to ensure that the project is still justifiable and should continue. Financial stakeholders in particular will be interested in understanding the health of the project to ensure requirements, benefits, and cost are maintained.