“Restrict Registration” is a plugin for WordPress that allows you to control 
who is registering on your blog. This plugin uses simple blacklists and 
whitelists to define who can register for your blog, and who is restricted. Use 
simple literal matching, flexible asterisk wildcard matching, or powerful 
regular expression matching: it’s your choice! The options page is clear and 
easy to use. Set your lists, and you’re done!
This plugin was inspired by WP-Deadbolt, but has been completely rewritten and 
redesigned, and several new features have been added.

Restrict Registration

Use simple blacklists and whitelists to control who can and cannot register on your blog.

Cyril Batillat

User restriction can be applied using multiple parameters :
<ol>
<li>IP</li>
<li>User ID</li>
<li>Embed URL</li>
<li>Or your own parameter, using plugin hook</li>
</ol>
Restrictions can be limited in time :
<ol>
<li>No limit</li>
<li>Daily</li>
<li>Weekly</li>
<li>Monthly</li>
<li>Yearly</li>
<li>Your own duration, using plugin hooks</li>
</ol>
Restriction message can be customized on each form.
Multilingual : english and french translations (.pot provided).

Gravity Forms User Restrictions

Restrict the number of user submissions on Gravity Forms

Restrict Registration vs Gravity Forms User Restrictions