united-states california federal-courts legal-citation
Citing federal court cases as authorities in state court
<p>Do federal court rulings (non-appeal) function as estoppel or persuasive authority for them to be cited as authorities in state court civil complaints when the question at stake relates to state laws?</p>

<p>That depends what the issue is. On constitutional issues, and on issues of federal law (which do come up in state cases) , they are binding  precedent, at least in that circuit for an appeals court opinion, and in the whole US for a Supreme court opinion. District court opinions are not generally binding unless upheld on appeal. On matters of state law, the state's own highest court is the final word, but a federal opinion could be at least as persuasive as one from a different state.</p>
<p>to the best of my understanding one does not use the term &quot;estoppel&quot; to describe the effect of a previous judgement by a different court. If it is in the same case and not on appeal, the term is <a href="https://www.law.cornell.edu/wex/res_judicata" rel="noreferrer"><em>Res judicata</em></a> (&quot;A thing (already) judged&quot;). If it is a general matter of adhering to clear precedent, the term <a href="https://www.law.cornell.edu/wex/stare_decisis" rel="noreferrer"><em>Stare decisis</em></a> (“to stand by things decided.” ) would be used.</p>
