以上 ②・上は・からには: the difference
以上 ②N2
Meaning
Since, Now that, As long as, If
Past papers
Tested 5 times in past papers
Example
試験を受ける以上、休むことはできない。
Since I'm taking the exam, I can't skip it.
上はN2
Meaning
Once, Since, Now that, As long as
Past papers
Example
かくなる上はきさまを殺すしかない。今すぐ。
Since it has come to this, I have no choice but to kill you. Immediately.
からにはN2
Meaning
As long as, Since, Given
Past papers
Tested 4 times in past papers
Example
二十歳になったからには、自分の行動に責任を持たなければならない。
Now that I've turned twenty, I have to take responsibility for my actions.
How to tell them apart
「以上（は）」: the most common; duty arising from a status or an agreement.
「からには」: stronger personal will and determination.
「上（うえ）は」: the most literary; 'it has come to this, no way back'.