Sometimes, but only to a limited extent. Gaussian blur can be partially reversed with deconvolution or inverse filtering, especially if you know the original blur radius (or point-spread function) that was applied. Methods mentioned include inverse filtering, Wiener filtering, and Richardson–Lucy deconvolution.

The catch is that blur removes image information. If you don’t know the exact blur settings, or if the files were saved as 8-bit images and/or compressed as JPEG, recovery becomes much less effective. In those cases, blur-reduction tools may give a slight improvement, but they usually won’t restore missing detail well enough if the images are heavily blurred.

So the practical answer is:

• If you know the blur radius, try deconvolution/inverse filtering.
• If you don’t, a Wiener or commercial blur-reduction tool may help a little.
• If the images are very blurred and only low-quality copies remain, the lost detail may simply no longer be recoverable.