いいわけないだろ -- I'm not sure how to translate it properly


I came across the phrase which I wrote in the title while reading a manga and
I don't get it very well. At first I thought it was actually 言い訳 and the
author didn't want to use kanji but after reading a few examples when I
searched sentences, it's actually 良いわけない, so it would roughly translate as
"That's no good"? Let me give a little bit of the context.  
It's about two teenage boys and they have magic powers. Let's call them A and
B. Each boy can summon a magical weapon. A is a better magic user and can
wield his weapon very well while B is less trained, but at least he can summon
his weapon. B asks A to train him.  
*B summons/takes out his magical weapon and A says the following:  

> これ実家で保管してるやつでしょ？持ち出しちゃってよかったの？ (Is he saying "This the thing that is kept in
> your family, right? Isn't great that you can bring it out?")  
>

I know it's a very rough translation...And now B replies with:

> いいわけないだろ。早く使い方教えろよ。  
>

So, I get the last part ("Hurry up and teach me how to use it!'), but the
first one, I feel like he wanted to say "this isn't good" or even 'good
enough'. It's just this small part that I need to know to understand something
in regards to their powers.  
Can someone help me out, please?




So glad you have provided enough context. Look carefully the two parts in
**bold** below because 「いい」 responds to 「よかった」.

> A: 「これ実家{じっか}で保管{ほかん}してるやつでしょ？持{も}ち出{だ}しちゃって **よかった** の？」
>
> B: 「 **いい** わけないだろ。早{はや}く使{つか}い方教{かたおし}えろよ。」

Understanding A's last sentence would be the prerequisite to understanding B's
first.

In 「いいわけないだろう」, 「わけ」 means "reason", "grounds", etc. **You use this phrase
when responding negatively (and firmly) to a statement or question that talks
about whether something is good or not**. Please remember that we use this
phrase very often.

Thus, 「いいわけない」 means 「持ち出していいわけない」 here.

_**Literally**_ ,

> A: "This is the one that's kept at your parents' place, isn't it? Was it OK
> to take it out?"
>
> B: "There is no good reason (for doing that). Hurry up and tell me how to
> use it!"

To translate B's first sentence more naturally, I would use:

> "Definitely not!", "No way!", "Impossible!", etc.




So glad you have provided enough context. Look carefully the two parts in
**bold** below because 「いい」 responds to 「よかった」.

> A: 「これ実家{じっか}で保管{ほかん}してるやつでしょ？持{も}ち出{だ}しちゃって **よかった** の？」
>
> B: 「 **いい** わけないだろ。早{はや}く使{つか}い方教{かたおし}えろよ。」

Understanding A's last sentence would be the prerequisite to understanding B's
first.

In 「いいわけないだろう」, 「わけ」 means "reason", "grounds", etc. **You use this phrase
when responding negatively (and firmly) to a statement or question that talks
about whether something is good or not**. Please remember that we use this
phrase very often.

Thus, 「いいわけない」 means 「持ち出していいわけない」 here.

_**Literally**_ ,

> A: "This is the one that's kept at your parents' place, isn't it? Was it OK
> to take it out?"
>
> B: "There is no good reason (for doing that). Hurry up and tell me how to
> use it!"

To translate B's first sentence more naturally, I would use:

> "Definitely not!", "No way!", "Impossible!", etc.

