What is Romeo implying in these lines. The prince expressly hath forbid this banding in Verona streets

Romeo is implying that if Tybalt had obeyed the prince's orders, lives would be pulped, including his.

Explanation:

Romeo expresses how disobedience is evil and promotes pain and suffering. He reinforces that the prince had banned street fights, but Tybalt insisted on disobeying causing very negative results and that caused his own death, the death of Mercutio and exile of Romeu, who had to abandon his family and wife before being killed.

you should ask "yourself is it good enough? "