On the bing.com website it is possible to enforce safe search by adding &adlt=strict to the search string. An example is below.

https://www.bing.com/images/search?q=just+testing&first=1&tsc=ImageHoverTitle&adlt=strict

However the user can still turn off safe search on the top right by selecting the dropdown to turn it off. How can I pass some cookie or URL parameter to prevent the user from being able to switch safe search off?