ivy - it would be a pleasure if you would stick to one meaning, or, if you can't, to give two meanings in one question.
your original posting suggested that to protest against is equivalent to 'to tackle', which I suggested is not the case, for the reasons I already outlined.
your last posting changes the suggestion to 'gegen angehen/protestieren', which at least has the benefit of including a correct meaning....
to sum it up:
to tackle a - means to take steps to stop, or change, something
to tackle a law - to take steps to stop, or change, or get rid of, a law.
protesting against a law might well be one strategy to get it changed, but it is not the only one, and not even one most likely to succeed, and it is *not* the primary meaning of 'tackle' -
a rough translation (scusi for any errors) might be: Schritte unternehmen um ein Gesetz zu Fall zu bringen/ ein Gesetz zu ändern