@TinTin
If that's the case, the entire "right to roam" movement in England makes no sense at all.
If I can relate the situation in Italy, it is basically the same. First, you always have the right to walk in every trail which is signed on the IGM maps. In those, free walk cannot be denied, even if they are in a private property.
Second and as a general rule, you always have the right to bivouac for the night, unless some specific norms apply.
The only cases I know of not being able to camp are:
a) private property, and this is extremely questionable if it is along a trail; Even if the property is fenced, it there is a trail crossing it you have the right to get in, so there is never the question of "trespassing", only of the proprietor to ask for money, which generally goes from €3 to €10 per night or so depending on zones or periods.
b) reserves, parks, conservation areas where a specific norm prevents bivouacs. Not all of them prevent bivouacs. E.g. the
PNALM forbids bivouacs, but the
Parco Regionale dell'Adamello, or the
Riserva Naturale Navegna e Cervia, explicitly allow bivouacs.
c)
Region Valle d'Aosta prohibits bivouacs below 2.500m of altitude (!);
d) Region Piemonte prohibits bivouacs blow 800m of altitude.
All the rest of Italy is fair game as far as bivouacs are concerned, unless you are inside a reserve, in which case you must ask the reserve. Most likely, you notify the Reserve of your passage. If a certain number of hikers is surpassed, the Reserve will deny you the right to bivouac.
Basically the simple rule I have for Italy is "stay clear from Valle d'Aosta, check if it is a reserve, check the rules of that reserve". That's all.
Free camping on the other hand is always subject to authorizations, but that's another story.