It isn't easy to overturn state or federal laws but it is far from impossible.

Here are a few examples.

Gregory Watson got the constitution amended in 1992[0].

Reverend Warren H. Stewart got Arizona to declare Martin Luther King day a state holiday[1].

Richard and Maureen Kanka got Megan's law passed[2].

[0] https://constitutioncenter.org/blog/how-a-c-grade-college-te...

[1] http://archive.azcentral.com/arizonarepublic/news/articles/2...

[2] https://en.wikipedia.org/wiki/Megan%27s_Law