On the other hand, the opposite model might be worth consideration. Invoke a subscription pass or fee for those who access archives from within the site, but let outside sources link to individual archived articles with permanent URLs for free. If I'm reading other messages correctly, that's something akin to what WashingtonPost.com is doing and touting it as a feature, although I don't claim to know their details. Basically, once you've found an article, the access to it would be unlimited, but if you need to use the site's own search engine to find it, you'll pay for the service once you retrieve the full article. (Why not go to Google and look first? Good idea, but some people aren't savvy enough to think of that, or if they are, wouldn't be able to narrow the search results to the desired domain. If the host site's search engine allows an easier, more specific, and up-to-the-minute search, people might still have incentive to use it.)
So while you may "get away" with this approach initially, ultimately you'll be poisioning your ranking status with the search engines -- probably even for your home page. I'd advise against the practice.
Chris ShermanEditor, SearchDayhttp://searchenginewatch.com/searchday
Use your imagination and you'll probably think of all sorts of devious variations on this concept that might further one's business agenda. The Google link leads to the article for free; the weblog link that criticizes my newspaper's professionalism produces a premium entry point.
Disclaimer: Use your own discretion when applying this concept. My own ethics prohibit me from practicing all the tricks which I am often clever enough to think of. :)