From the standpoint of US law professors, where Westlaw is dominant, this presents a significant problem.Citation counts of faculty productivity are done through Westlaw. As a result, scholars and practitioners looking to have a larger impact will have fewer incentives to submit works to OUP journals as they will be punished for doing so with fewer citations. Moreover, the W&L journal impact factor counterof journals is also based on Westlaw.
The problem is more serious than just cite counts. This will affect both authors and researchers. Most people I know (myself included) exclusively use one legal database. In my case, that's WESTLAW. The only time I go to LEXIS is to use NEXIS to access newspaper and magazine sources unavailable on WESTLAW.
So let's say I want to find any law review articles that have been written on corporate governance standards for microfinance companies. I log onto WESTLAW, click to the JLR database and run a few searches. Then I'll hop on SSRN to see if there are any recent working papers. But I'm not going to go on to LEXIS, because 99% of the time the search will kick up duplicate results.
But because OUP journals now are unavailable on WESTLAW, I'll miss any articles published therein.
As an author, I don't want people missing my articles because the journal is not in their search engine. As a researcher, I don't want to have to run the same search (albeit using moronically different proprietary search codes) in multiple databases.
According to Leiter, OUP claims that they are "very keen to ensure that all our journals are discoverable and citable." If they were, they'd have their journals on WESTLAW. My guess is that what they're really very keen to do is to maximize the revenues from their new "preferred licensing partnership deal with Lexis Nexis."
But, then again, who am I to complain when somebody decides to do something revenue maximizing?