BRIOSCHI Elfrida Consultant said:
I knew that you cannot block an admin because he can simply unblock himself. There were some experiments on it.wiki (have a look to http://it.wikipedia.org/wiki/Speciale:Log/block), but I cannot understand if there's a problem or is the right behaviour.
This is the expected behavior of the MediaWiki software.
Whether it's allowed is a matter for policy. For instance the English Wikipedia currently has blocks for users who revert an article more than three times in twenty-four hours. The policy on that particular Wikipedia explicitly states that an admin should not unblock himself if blocked for this reason. Also blocking only affects editing. A blocked admin on Mediawiki can still use his admin powers (for instance rollbacks, to perform the equivalent of reverts.)