LexisNexis, which does other things now but started in the legal space, offers a huge collection of legal opinions with a fairly good search and linking capabilities. Most clerks and law professionals would have access to it.
I think the benefit of Wikipedia is not access to materials so much as it is the succinct summarization of the legal opinions. Perhaps now NLP could help with this, but it's a very complicated problem to provide a summary of the important bits from a 100+ page legal document.
> ... the succinct summarization of the legal opinions.
LexisNexis and Westlaw produce succinct summaries of legal opinions. That's the basis of their value, because the legal opinions themselves are not copyrighted. They also categorize everything about an opinion so that their database is searchable by area of law, etc.
I think the benefit of Wikipedia is not access to materials so much as it is the succinct summarization of the legal opinions. Perhaps now NLP could help with this, but it's a very complicated problem to provide a summary of the important bits from a 100+ page legal document.