Dear Brother, assalaamu alaykum. In my country, people of many states primarily still use coal as fuel to cook their foods and make bread, biscuits, and other items to sell, and almost all the items found in the markets, hotels, and shops that require cooking or baking are usually made using coal as fuel, so there is no way without coal. The problem is that besides giant industries, all other small-scale industries, small road side hotels, restaurants, etc. buy their coal from "cycle coal wallah" (people carrying coal bags on their cycle to sell). These cycle coal wallah get their coal from mines illegally, or by stealing, or by digging abandoned mines, (as read in various survey articles), and maybe some also buy it legally. My question is: is it haram to buy products made with stolen or illegally mined coal? Can I buy products from the market knowing that the root of the coal from which the product is made is illegal? Please answer Sir, and do not that I suffer from OCD (Obsessive-Compulsive Disorder). May Allaah reward you.

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger. 

You asked, “Can I buy products from the market knowing that the root of the coal from which the product is made is illegal?”

The answer is: Yes, you are allowed to buy the products from this market. We ask Allah to bless you with recovery from OCD, which you are suffering from.

You have to keep in mind in all your affairs that the basic principle is that things are lawful unless proven otherwise by Sharia evidence. You are not required to investigate and ask about the source of things, as this entails hardship, and Islam alleviates hardship; Allah, The Exalted, says (what means): {and He (Allah) has not placed upon you in the religion any difficulty.} [Quran 22:78]

If this basic principle should be followed by the regular people, it should be followed by those who suffer OCD with greater reason.

Allah knows best.