A crime is a crime, is a crime. You would have to ask who determines that it is for "public welfare" and what is "valid". There are laws that tell you what you can do under specific circumstances, therefore, if it is legal under certain cercumstances it is not a crime. But if a person decides to play, say Robin Hood, robbing stores to give to the poor, there is no law that justifies that even if Robin Hood thinks he is doing so in the interest of public welfare and would certainly end up in jail. There is a reason for laws so that each person does not get to determine what crime they can commit in the interest of what they believe is "valid"