What law? Which jurisdiction?
Here’s another one, I haven’t tried it yet though.
Every serious legal document I have ever signed required either my being there in person or providing a Medallion Signature Guarantee. I won’t explain what that is since it isn’t relevant here. By “serious” I mean documents transferring ownership of financial instruments.
For something like a contract or tax form, a scanned signature will probably suffice if the person receiving the signature is willing to assume the risk that it may be forged or is otherwise not being provided by the person identified by the signature.
Encryption isn’t an authentication mechanism. It’s a confidentiality mechanism (and, with PKI and such, a non-repudiation mechanism).
Title 18 (Controlled Substances Act), for one, in determining the difference between “digital” vs. “electronic” signatures for things like Schedule I drug manufacturers moving dangerous drugs to distributors, and then on to retailers. There was a lot of industry feedback that came out of the proposal in the Federal Register. Somewhere around here I have a whole ppt slide deck that I put together on the subject.
It can also be used for authentication. Google ‘PGP authentication’.