The bylaws also prohibit going shirtless or in a bikini in areas away from the beach, a ban that was introduced several years ago in Barcelona to little effect as offenders are mainly tourists who fly home without paying the fines.
That’s easy to solve. You confiscate the passport until the fine is paid. Or arrest them and hold them without bond as a flight risk. The last time I got a speeding ticket–about 15 years ago, I think–I was in Ohio, and driving home to Illinois. The cop took my license, and said they’d mail it back once I paid the fine.
Quick edit: I’m not talking about cash bail here; that’s a separate issue. Bond can be refused when a suspect is deemed to be unlikely to show up for court, such as the suspect being a foreign national. This happens regularly, and isn’t particularly controversial. A person that is a citizen and resident of a foreign country is very likely to skip out on criminal penalties, therefore they shouldn’t be permitted to leave without paying their criminal fines.