Anyone here with any experience of locking-down a website to registered users only and locking-out all search engines?

About 10 years ago I considered this but instead simply removed that site and all its information.

For the past 28 years both the trade and Joe Public has haccess to my sites however I'm bored with Google's continual antics therefore considering access only to bona fide exisiting and potential new trade clients.

We have a very large global contact database therefore can advise of this move ... The other alternative would be to remove all product information leaving a single splash page with brief details and contacts.

I would not be the first to do this in my industry, in fact four of the largest Indian widget producers have already been doing this since 2015/6 with no adverse affects whatsoever and I'm pretty certain my other directors would have considered this if it were not for the fact I create and maintain the sites.