Buying a sword for decorative or ceremonial purposes is generally legal in India. However, the Arms Act of 1959 and the Arms Rules of 2016 govern the possession, carrying, acquisition, sale, import, and export of arms and ammunition in India.

While swords aren't specifically mentioned in the Arms Act, they could potentially be considered arms under the legislation, depending on their characteristics or the manner in which they are used. For instance, a sword that is capable of causing death could potentially be considered a weapon, and the possession and carrying of weapons are regulated under the Arms Act.

Furthermore, state laws and regulations might impose additional restrictions or requirements. Also, even if it's legal to buy a sword, carrying it in public might be regulated or even prohibited, as it could be perceived as a threat to public safety.

If you're planning on buying a sword in India, I would recommend consulting with a legal professional to ensure that you're in compliance with all relevant laws and regulations. Please note that this information is based on my training data up until September 2021,