You're getting a lot of responses to the effect that there aren't really any laws that require particular formalities to sign contracts, and while this is true in the "normal case" in many jurisdiction, there certainly are some categories of document that have more specific signing requirements. In most common law jurisdictions, for example, certain agreements must be signed as deeds which require certain formalities to be observed, and without enabling legislation it's not always easy to square these formalities with electronic signatures.

https://en.wikipedia.org/wiki/Deed