Apt translation from Swedish?

[Douglas G. Wilson]

A correspondent asks:

"Do you know if there is an English word or expression for the Swedish term
'rättshaverist'? This concerns a person who considers himself maltreated by
a more powerful party, usually a company or other authority, and continues
to fight for his right long after most people would give up, even after
losing a court case, with appeals."

My best answer is "courthouse castaway".

Any improvement available?

-- Doug Wilson