can a diplom in civil engineer can do a structural design of any type of commercial, apartment buildings?

can a civil diploma holder( from india) working in a structural engineering company for past 10 years and designing various types of building, can do his own practice as a structural engineer? or it is necessray for him to get a registration from any institutions, because it is not possible for further studies to get any degree, or AMIE Membership by attending exams.

mere experience or certificate from the company where he's working for past 10 years and his boss knows his ability and experience as well as his service for the company? can anybody help me?( it woud be better if the person is from india who knows the situation better) also if it is illegal to practice privately, what is the next step. he's 42 now and the people who know me very well( builders, etc,) asking me to do their projects and not from the office where he is working. please help me. if there is any online course or certificate course and anybody who can give me the certificate ? looking for a genuine answers.