I have finally managed to read all of the paper I linked to, and I think the author is fighting an uphill battle. Some of the terms he mentions are correct (i.e., definitely wrong in standard  English), some are bad style, perhaps, but not necessarily wrong, and in some cases the meaning has simply shifted away from what he might have grown up with, or words are used in a specialist context that he may not be familiar with, or just doesn't like.
In my opinion he quite often fails to properly distinguish between "plain wrong", "bad style" and "might not be fully understood by an average native speaker". Bearing that in mind, legal language is always a specialist language, regardless of the actual language being used. Just because it's (legal) German doesn't mean that your average German will necessarily understand it (fully), either. (This fact is seldom appreciated by laypersons, however, thinking that they do recognize the words, after all, and just how hard can it really be?)
This document, such as it is, is an odd mix of a list of false friends, style guide recommendations and a primer on "how to be understood by laypersons" (which may or may not be your intended audience). Interesting reading, to be sure, but to be taken with a grain of salt.
 whatever that may be