It is difficult to control or stop others from other countries to sell to another countries. Even there is no law to stop one from importing product and sell in country, bypassing the authorized distributor. The only thing they can do is just to track the serial number and honor warranty based on that. However, many still willing to buy gray market product since they believe a high chance that the product will not break within that warranty period.

Gray import by unauthorized seller, I meant. You cannot stop them. They only provide warranty through them. They sell cheaper price and customers know it. This is common even for branded product. Not only here but also in the US.

There is no law to stop it. The product is not fake either. Willing buyers will buy. Others who want warranty by manufacturer will avoid. Many seller like this on online shops. It is stated if the warranty is by local manufacturer or by seller. If in doubt, you can ask the seller. They will tell based on my experience.

If price is too low, probably fake product.