Is it legal in Italy to add this charge if it's not disclosed on the menu? In four previous trips I've never had this added only except when it was listed clearly on the menu. This past May it happened three or four times. In one case the charge was 3.5 euro per person and the young couple at the table next to us we're very upset because they'd figured the cost of their bill very carefully and with the extra charge they didn't have enough to cover the bill.
"Listed clearly on the menu" is a matter of judgement. In my experience it's always somewhere on the menu.
Since 2007 it has been illegal for restaurants in Rome to impose a cover charge. Some try to get round this by charging for bread so if you don't want the bread send it back and make sure it does not sneak on to the bill.
http://en.turismoroma.it/roma_ti_accoglie/dove_mangiare/i_consigli_per_una_buona_tavola
"Listed clearly on the menu" is a matter of judgment. In my experience it's always somewhere on the menu. Actually it's more a matter of reading something printed on the menu rather than judgement. In all four cases we got the menu back and is was not listed anywhere.