Can I reserve a beach spot by leaving an umbrella and lounge chair overnight (Italy)?

During August the beaches in Italy are notoriously crowded and unless you arrive early (and we're talking before sunrise in some places), you cannot get a spot close to water.

I have observed that European holiday makers in these locales will place an unfurled umbrella and lounge chair at a prime spot the previous evening. This appears to be a signal that says "this place is reserved, pick a different spot". Sometimes this is also done by laying out two beach towels overnight. Apparently this is a widely observed convention that follows an unwritten rule: if somebody puts something there, the spot is reserved. The occupiers appear after after a leisurely breakfast to a prime spot.

I understand that some northern European tourists can be quite aggressive about enforcing this unwritten rule in southern Europe, to the extent of threatening police action if their stuff is moved or disturbed.

Notwithstanding the risk of theft, since an umbrella can be covered by travel insurance, is this a viable strategy?

Question: does it work to leave an unfurled umbrella (or other beach gear) set up on the beach overnight? Does it violate any regulations, for example on the west coast of Tuscany? Or the other way, can people get in trouble if they disturb your stuff which has been used in this way?