As usual, a lot will depend on your target audience. If this is one lawyer writing to another, then the archaic use of "instance" could be justified. However, if this is for a more general readership then the triumph, in Britain at least, of moves to make legal language more accessible to the general public, such as the Campaign for Real English, should be taken into account. In which case I would simplify it as much as possible.


Trying to get my head around what is being stated here I would go for the sentence below. It may lose some "matices" - but I think it gets over the essence. Though I am willing to be corrected by colleagues with more experience in the field.

"...may consider whether there has been a breach or not, but in any case the argument put forward by the Committee of Experts in their initial interpretation should be countered first."