Acho que o melhor artigo que vi sobre isso é Corporatetravelsafety.com :
They begin the Paris String Scam by engaging you in innocent conversation and will usually say that they want to show you a magic trick. Before you know it, a "string man" has grabbed your wrist or one or two fingers and encircled it with a homemade bracelet of colored string. You think the conversation or interaction is an interesting way to meet the "local flavor" of Paris and you allow them to engage you in what seems like an innocent act of being charmed by the "locals."
Isso acontece em toda Paris, e especialmente (obviamente) em áreas altamente turísticas. O golpe então é "cobrar" você por essa pulseira que você não tinha intenção de querer:
While the Paris String Scam may be fun to watch, when the string men finish making your new "local Paris string bracelet souvenir," the string men will demand payment of around €20 Euros when they are finished, which is quite obviously not what the bracelet is worth. If you fail to pay them, they will doggedly follow you and be VERY insistent that you provide some amount of payment.
Também é comumente usado como uma distração, enquanto um companheiro dos seus pick-pockets você.
Então, alguém sendo abordado pela polícia pode ter sido um desses picareteiros. Ou, indiscutivelmente, vender mercadorias sem licença, embora pareça improvável que a polícia vá abordar um cara para isso (embora você também a veja na ponte de Westminster em Londres - a polícia aparece, todos os agenciadores saem correndo).
Como lidar com eles? O mesmo site oferece isto:
If someone approaches you with the words ‘for the church’ or ‘bracelet’ or ‘gift’ or 'magic' or 'trick' and they are carrying strings, just put your hands in your pockets and keep walking. For those string men who are more aggressive, politely say "Non, merci" but most importantly - keep on walking - do not stop. Be courteous but firm, and the string man who's targeted you will usually then move on to the next victim. If you really want a string bracelet as a souvenir, you can easily get one free: Just pick up strings that unhappy tourists have discarded on the steps leading up to the Basilica.