In 1999, the European Parliament passed the European Directive 1999/93/EC as law. This directive stated that electronic signatures (e-signatures) would bear the same legality, authenticity, and validity as pen-to-paper signatures. In 2001, all member nations of the European Union agreed that e-signatures would be accepted as legally binding both domestically and internationally. With this agreement, the European Union's Court of Justice agreed to treat e-signatures as legally binding in many areas of commerce.
There are a few exceptions in some locations to the laws passed by the European Union. For example, the purchase of property, and marital papers. There may be other exceptions to this law in different regions.
In the US
In June 2000, the United States Congress passed The Electronic Signatures in Global and National Commerce Act into law. This is also known as ESIGN (Pub. L. 106-229, 114 Stat. 464, enacted June 30, 2000, 15 U.S.C. ch. 96). This law recognises all verified e-signatures as legally binding and valid. Like in the European case, there are a few exceptions to this law and one must look into these if they are unsure.
Tip: If you are unsure on whether your document can be signed electronically or not, the information can be found in many law documents.