The concept of a lacuna in the law does exist:
In law, a non liquet (commonly known as "lacuna in the law") is any situation where there is no applicable law.
I imagine this is what’s being referred to in the sites you link, even though there’s no definite article—headline style would omit the article, for example, or possibly the “law” being referred to there is an abstract noun.
At any rate, this sense of “lacuna in (the) law” isn’t exactly what I (a non-expert) generally understand by “loophole.”
P.S.: Loopholes are a subset of lacunae. A lacuna describes every specific matter about which no law exists, but a body of public, judicial or academic opinion believes it should, to address a particular issue (often described as "unregulated" or "wholly inadequately regulated" activities or areas). A loophole, where properly defined by contrast, denotes that a set of laws addressing a certain issue exists, but can be circumvented (or is being exploited) due to a technical defect in that law. [Wikipedia article linked above.]