If bitcoin is illegal on your country , you can still use crypto only online because country or a government rather dont hold the online world , they dont hold bitcoin but its possible that they can ban some sites within their network or within the countries local ip . there are also sites that are illegal online and you can get into some serious trouble if you will insist to use and visit them .
If bitcoin were illegal in the country then you must obey the law with your government because if you have been caught of course you must punishable by them. So, you don't have anything to do if illegal in your country unless you migrate into another place were bitcoin was allowed to use.