Electronic signatures and law

Worldwide, legislation concerning the effect and validity of electronic signatures, including, but not limited to, cryptographic digital signatures, includes:
European Union and the European Economic Area.
In the EU, electronic signatures and related trust services are regulated by the Regulation (EU) N°910/2014 on electronic identification and trust services for electronic transactions in the internal market (eIDAS Regulation). This regulation was adopted by the Council of the European Union on 23 July 2014. It became effective on 1 July and repealed the Electronic Signatures Directive 1999/93/EC. At the same date, any laws of EU member states that were inconsistent with eIDAS were also automatically repealed, replaced or modified. In contract to the aforementioned directive (which allowed the EU member states to interpret it and transpose it to their own law) the eIDAS Regulation is directly effective in all member states. 
Before eIDAS.
European Union Directive establishing the framework for electronic signatures:
New Zealand.
For an overview of the New Zealand law refer:
- "The Laws of New Zealand", Electronic Transactions, paras 16-18; or
- "Commercial Law", paras 8A.7.1-8A.7.4. (these sources are available on the LexisNexis subscription-only website)
United States.
Case law.
Court decisions discussing the effect and validity of digital signatures or digital signature-related legislation:
Uruguay.
Uruguay laws include both, electronic and digital signatures:
Turkey.
Turkey has an Electronic Signature Law TBMM.gov.tr since 2004. This law is stated in European Union Directive 1999/93/EC. Turkey has a Government Certificate Authority - Kamu SM for all government agents for their internal use and three independent certificate authorities all of which are issuing qualified digital signatures.