If he_____ guilty,he shall have the right of appeal.
were found和be found.
在书面语中,if 引导的条件句表示推测时,谓语动词可用 be 型虚拟式。如:
If John be found guilty, he shall have the right of appeal. 若约翰被判有罪,他有权上诉。
(摘自赵俊英:《现代英语语法》p.344)
所以,网友的句子应该填 be found :