Originally Posted by NALEM

If they are a regular or premium supplier of paid links, there is always an agreement that is required for them to sign, acknowledging that they have rights to post such links on XYZ sites, and the terms are: ________________________.

I've never done this for "links" but for all other purposes of services, if the amount is considerable, and I have people in that persons country, than I will put the effort to remind them of the terms, and if needed, file a police report in their country, and possibly have a local reach out to them.

Otherwise, if I have no one locally, and the monetary value is insignificant, than its considered a loss, and the most I will do, is blacklist them internally, and post my frustrations on a site like GFY.