Manual:Block and unblock

admins>Special:MyLanguage/Manual:Administrators|Sysops can block and unblock IP addresses (and registered user accounts if username blocking is enabled) from editing, uploading files, moving>Special:MyLanguage/Help:Moving a page|moving pages, and, if they have been granted such rights, protecting/unprotecting and deleting/undeleting pages.

It is important to remember that blocks are preventative, rather than punitive.