This following idea may, or may not, be aligned with your purpose. I imagine a fair percentage of visitors come just looking for answers to their questions, rather than getting involved with a discussion. So, not having a search tool available would tend to discourage that sort of research.
I would suggest that the search feature at least be available to new registrants without having to create 25 postings first. Actually, I prefer that it be available even to visitors. I realize you need some sort of protection to prevent automated abused of the search feature, but there are ways around that. For instance, requiring a "I am human" sort of test, or simply a 15 second wait between searches.
Of course, requiring the 25 posts first, may encourage people to participate in the forum. But, it will also discourage people from using the great resources on this forum. Without a search tool, it is like an encyclopedia where the articles are scrambled. The info is there, but so buried, it cannot be found.
My purpose in coming here, was to find the quotes that Bob Enyart cited in his broadcast. He was quoting from a medical dictionary, and showed how the definition of conception has changed for political reasons. I eventually found the info on another web site, since it was not possible to search for it here.
If you decide to leave the search restrictions in place, or perhaps the software just does not permit you to change it, please consider making the reason more apparent to the user. The existing "you don't have permission" does not indicate that you need 25 postings before you are permitted to do searches.
-Joe