In this task, we ask you to rewrite a sentence in simple English without changing its general meaning. Essentially, you want to make the sentence easier to read by using simpler words, utilizing more straightforward sentence structures, and omitting non-essential information etc.

Landmark court decisions , in present-day common law legal systems , establish precedents that determine a significant new legal principle or concept , or otherwise substantially affect the interpretation of existing law .
A Landmark decision , or Landmark court decision , establishes new precedents that establish a significant new legal principle or concept .