[Avodah] violating a lav to perform a mitzva

[Shaya Potter]

on areivim it was stated

"admittedly, one is permitted to free a slave in order to perform a
mitzvah, even a
rabbinic mitzvah like constituting a minyan"

how does this fit w/ mitzva ha'baah b'aveirah.  Based on the gemara in
sukkah (a stolen lulav can not be used for the mitzva of lulav) this
strikes me as strange....

what are the parameters of the above statement?