Murphy's law, Betteridge's law, or other facetious laws are at least roughly formulated as "if X, then Y" (or sometimes "Y happens"), which mimics the structure of actual scientific laws. Stallman's statement is formulated as "if X, then maybe Y" (or "Y could happen").
Well he did, so apparently you can.
Also, you definitely can, tongue-in-cheek, call a general statement a "law." It's not meant to be taken in a literal sense; it's meant for humorous or broadly pragmatic effect.
"If corporations write the laws, then maybe they will restrict or mistreat their users." That's not a law.
As soon as profit maximization is at odds with the user's interests (that's pretty much all the time), the corporation will naturally act against the user's interests.
From this, I'm pretty sure "law" is a relatively accurate descriptor.