As Brietta says this is not only about the legal right but 'moral right' to spend publicly donated money in a way that is not within the stated aims of the fund.
I am a member of the public who has donated to the fund. I have no problem with how my money was spent - or will be spent.
This is because I have no reason to believe there is anything fraudulent about the fund, or that the McCanns are 'innit' for the money. People who are greedy for money don't put hundreds of thousands of pounds, which they could quite legitimately put into their own bank accounts, into a fund. Neither do they donate to charity thousands of pounds which they also could keep for themselves. Neither do they hand over hundreds of thousands of pounds to expensive PI companies - when all they had to do was say 'No - we prefer not to employ them - we are happy with our own employees'.
Just another example IMO of the McCanns doing the complete opposite of what guilty people who are greedy for money for themselves would do.
The ability of some to convince themselves that black is white never ceases to amaze me.
AIMHO