So long as the jurisdiction in which they are signed accepts digital signatures, and the signature was produced using an accepted secure method, then maybe - consult a lawyer.
Although, this standard may not even be required, if the signature in question is not contested. Just think of all the legal documents all of us have signed, and then faxed to some destination - the receiving end has only a printed copy of a digital representation of that document, and those can be successfully defended legally.
Some people wonder about this because of the supposed ease with which a digital image of a signature can be replicated (it would seem that forging a digital signature would be as easy as copying an image from the internet - it's just a file, right?), but the law is able to handle these situations, the technology has built into it ways to detect if signatures are copied and/or manipulated, and the reality is that very few signatures are ever contested anyway, and so in most cases the technology behind how the signature was created never comes into question.
Many banks, for example (I used to work in the banking industry) have digital signature devices where you write on a screen instead of with an actual pen, and these are completely valid. Federal law (in the United States at least) also allows a digital copy of a paper check to be considered equally valid vs. the paper equivalent, due to sufficient mechanisms that allow for the origin and validity of said image to be verified, should it be contested (again, very few of them, vs. the total number of checks processed, are ever contested anyway so this is often a non-issue).
Finally, digital signatures that are not representations of written signatures, but instead simply a typed name, combined with some secret only the actual signee would know (a PIN for example - I digitally sign my Federal tax return this way every year) serve to prove the authenticity of a digital signature. There are also many technologies within the cryptography community that are focused on digital signatures, and which come with methods for detecting forgery and manipulation.
If perhaps you're wondering whether a physical signature is more difficult to forge than a digital one (and I realize that I'm probably going way past the original scope of your question at this point), that's simply not the case.
