Do you need to know are bitcoin miners illegal? There is no simple answer to this question, and it all depends on what country you are in. In many nations, bitcoin miners are required to be licensed, otherwise it is considered an illegal activity.
Because commercial bitcoin mining uses a lot of electricity, governments want to have oversight of bitcoin mining operations.
Some countries, like India, haven't banned bitcoin mining, but they don't allow bitcoin to be used as money, or traded at exchanges in the nation. Other countries, like Iran, require that bitcoin mining operation are given a special license, or they will be considered illegal.
In most Western nations, like the US, UK, and Canada, mining bitcoin is totally legal, but will require permits, and also will be taxed like any other commercial operation.
If you are considering the development of a bitcoin or other crypto mining operation, it would be a good idea to talk to a lawyer that understands the crypto laws in your nation. There may be special requirements, if you want to ensure that your business is on the right side of the law.
Keep in mind that cryptos may not be considered to be cash by the tax authorities, which makes understanding the tax laws that would apply to mined tokens very important.