They are literally citing the law. That’s better than a link because links change all the time, but the citation remains valid because it’s referring to a code section and not some ephemeral html.
Depending on what you’re looking for (law or regulations), the official sites are code.house.gov or the Electronic Code of Federal regulations (ecfr.gov).
In January, it was going to jump to a minimum salary of 59k to be exempt.