～以上（は）
now that / seeing that
～以上（は）（いじょう（は））follows a plain-form clause and means “now that X is the case” or “seeing that X”. The first clause states an established fact; the second clause draws the obligation, resolve, or natural conclusion that follows from it.
The second half therefore tends to end in expressions of duty or determination: べきだ, なければならない, つもりだ, わけにはいかない. It is close in meaning to ～からには, but ～以上（は）sounds a touch more formal and written.
1. An obligation that follows from a fact
Given who or what someone is, a certain behavior is naturally expected.
学生である以上、勉強すべきだ。
“Now that you are a student, you ought to study.”
- 学生（がくせい）= student
- である = to be (formal written form of だ)
- 以上（いじょう）= now that, seeing that
- 勉強すべきだ（べんきょうすべきだ）= ought to study
2. A determination that follows from one's own act
After a verb in the past tense, ～以上（は）often introduces the speaker's resolve: having done X, backing out is not an option.
約束した以上、最後までやります。
“Now that I've promised, I'll see it through to the end.”
- 約束した（やくそくした）= promised
- 以上（いじょう）= now that, seeing that
- 最後まで（さいごまで）= to the very end
- やります = will do (it)
How to form it
Verb plain form + 以上（は）; nouns and な-adjectives take である + 以上（は）
- 引き受ける（ひきうける）= to take on → 引き受けた以上（ひきうけたいじょう）= now that (I) have taken it on
- やる = to do → やる以上（やるいじょう）= as long as (I'm) doing it
- 学生だ（がくせいだ）= to be a student → 学生である以上（がくせいであるいじょう）= now that (you) are a student
Key idea
～以上（は） says: the fact is settled, so act accordingly. Once X is true, the speaker treats the duty or resolve in the second clause as the only reasonable consequence.
Other N2 grammar
Updated .