This is a temporary measure and we will inform you once it becomes unnecessary. We hope that further restrictive measures will not have to be adopted as a result of putting such measures into effect.

I take it it was the first sentence that was causing you the main problem.

HTH

Alison

This is a temporary measure, and we will inform you when it is to be abandoned. We hope that such action will make the introduction of even stricter measures unnecessary.
Frankly, I think the writer ought to be the one to rewrite it - only s/he knows what s/he meant....

This is a temporary measure and we will inform you once it becomes unnecessary. We hope that further restrictive measures will not have to be adopted as a result of putting such measures into effect.

Suggestion:
This is a temporary measure which will remain in effect until you are informed that it has become unnecessary. It is our hope that further restritive measures will not have to be adopted as a result of putting such measures into effect.

This is only a temporary measure. You will be notified as soon as this measure becomes unnecessary. By putting such measures into effect, we hope to eliminate the need for adopting further restrictive measures.

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Note added at 36 mins (2003-09-17 12:57:11 GMT)
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I wish we have the liberty to change some of the words (e.g. adopting further restrictive measure > imposing further restrictions), but as David pointed out, we really do not know the intended meaning.