I believe both WSJ and WAPO give you access to a certain number of articles for free before they start to ask you to subscribe. That's probably what is going on with those links. This is a growing practice with a lot of news sites.
This can result in oddities like being able to reach a link from one client (say, your phone) but not another (say, a laptop) because on one you may have used up your quota.
Sometimes a site will reset the count periodically. I.E., letting you read, say, 10 articles per month for free before they start to pester you.