Apparently the Court of Session in Edinburgh have a power called Nobile Officium that no other UK courts have. It allows them to basically send a letter that the PM refuses to.
So in effect if he refuses to send the request to extend article 50, they can do it on his behalf.
https://www.theguardian.com/politics/20 ... -extensionEdit: The gammons would go off their nuts if this happens, especially after that court ruling the other day. How dare Scotland interfere!