I have been asked a few times whether one can trust the kashrut of this or that rabbi.
Truthfully speaking, though, financial laws are just as binding as kashrut laws.
The prohibition on eating pork is not necessarily more stringent than "thou shalt not steal."
However, only very seldom have I been asked whether certain monies are kosher, whether it is okay to use them.
–Rabbi Adin Steinsaltz
From a recent lecture in Jerusalem