[homonculus1]

Whatever department manages the beaches should insert themselves into this practice to moderate it. Sell pretty glass display bottles that are more attractive than a bag or soda bottle, but happen to be tiny. This wouldn't work if it inspired enough people to start collecting to outweigh the savings from intervention.

[maury91]

99% of the beaches are unmoderated (is an island so we have a lot of them). Tourists are usually caught at the airport or boarding the ferry (only 2 ways for leaving the island). Sometimes they are also spotted while they steal sand on the beach by the locals, that stops them and call the police.

[londons_explore]

The government should sell little glass test tubes for $5 each (ie. A very inflated price compared to the 10 cents such glassware costs). Put a government logo on them and a serial number.

Then put up signs at beaches saying "Taking sand is illegal unless you do it in a government vial". Allow tourist sellers to resell the vials on the beaches.

Then at airports and ports, allow those vials to go out filled with sand. Ban the import of vials (probably no need to enforce, because filling tiny containers is unlikely worth it on a criminal scale).

It's a very low effort way to tax a product without requiring tax returns and paperwork.

[jacobwilliamroy]

Stamp their passports! No more Sardinia for them! Ever!