I know that the usage of 仕方がない has been discussed [here][1], but I had an additional question. If you say:

> X (affirmative)  より仕方がない

The translation as I understand it is that you have no other choice but to do X.  

However, is another way to think about this grammar as:

> X (negative)  は仕方がある

or would this sentence have a different meaning than the former? As an example from my textbook, could I change the following:

> 車がないから、歩いて行くより仕方がない
　
> ー＞
>
> 車がないから、歩いて行かないのは仕方がある。

Finally, is it implied that the subject of the sentence with the は particle is being excluded as the option that is wanted?

  [1]: https://japanese.stackexchange.com/questions/8231/how-do-these-3-ways-of-saying-it-cant-be-helped-differ