Some of their discussion on the mailing lists positions it as a strike in opposition to the proposed law.

It does seem to be generating some coverage in the Italian press, so might be partially successful if that was the objective (we'll see if that discussion does anything to derail the law).

edit: To clarify, "their" is the Italian Wikipedia-editing community, which seems to have voted something like 40-3 among active admins who participated to blackout the encyclopedia. The U.S.-based Wikimedia Foundation wasn't involved. Presumably the Wikimedia Foundation could force it to be turned back on (they own the servers, etc.), but so far are not intervening.