Calcutta High Court on Wednesday put a seal of approval on the state government's decision to make it mandatory for commercial vehicles more than 15 years old to be replaced with new Bharat Stage II-compliant models, if their permits are to be renewed.The transport department has stopped renewing permits of buses, minibuses and taxis older than 15 years. Some bus-owners had individually moved the court and filed a writ petition challenging the government's decision.