Meaning of からには in Japanese

Definition of からには

からには(karaniha)

Now that you have finished your task, you are free to go and play outside.

一時いちじ、私たちは敵てきだったが、和解したするからには、もう親しい間柄である。

At one time we were enemies, but we've buried the hatchet and we are now on friendly terms with each other.

わたしがここに来たくるからには、心配しんぱいすることはない。

Now that I am here, you don't have to worry.

If you try at all, you should try your best.

If you do it at all, do it well.

If you do it at all, try to do it well.

As long as you're here, you'd better take a bath.

If you do it at all, do it well.

Once you have reached informal agreement, you should enter into a contract with the other party.

What miraculous sign can you show us to prove your authority to do all this?