How do you find out the number of a blocked caller

You don't... it really is that simple. Without the court being involved.

What do you think they are 'blocked' ?

Many people just don't answer blocked calls. Then they give up calling. Is it someone harassing you? Not saying anything? Bill colector?

What do you think they are 'blocked' ?

If the sender types in a * and the right two digits before dialing the number their caller ID will be blocked to the person being called. And the Caller ID will show blocked. Google star codes or feature codes... be aware some of them carry a fee from your phone carrier.