[kh99]

I'm not sure what you mean by "persistent against all posts" - do you mean you just want them to answer once, or each time they post?

If it's the first one I don't know, maybe there's a mod out there. If it's the second one, you could create a plugin using hook newpost_process and something like this code:

if (in_array($foruminfo['forumid'], array(1, 2, 3)))
{
   $vbulletin->input->clean_gpc('p', 'accept_rules', TYPE_BOOL);

   if (!$vbulletin->GPC['accept_rules'])
   {
       $errors[] = "You must accept the rules before posting";
   }
}

then in the appropriate templets (showthread, newreply, and newthread I think), add something like this:

<if condition="in_array($foruminfo['forumid'], array(1, 2, 3))">
<tr>
   <td><input type="checkbox" class="bginput" name="accept_rules" value="true"/> I accept the forum rules</td>
</tr>
</if>

(You don't have to make it a table row of course.)

You also want to change the 1, 2, 3 in each case to the forum number or numbers you want this to apply to.

You could also make a javascript popup to check before it's submitted if you like that idea better.