Since 2013, residents in Spain with assets above a certain threshold are required to file the modulo 720 form every year detailing assets outside of Spain. The penalties for non-compliance are severe, and non-declared assets are taxed as an “unjustified capital gain”, to which additional penalties and interest apply.
Jordi Pujol’s 30 year undeclared fortune outside of Spain seems like a perfect test case for this new law, and it will be interesting to see if the prosecutors go after him using this route. If not, it would make people question the value of filing the 720 form. There are some possible constitutional issues with the law (invasion of privacy, presumption of guilt, etc), so it will be a good test to see how much the Spanish government really believes in the enforceability of this law.