What is the test for a prisoner to make a First Amendment claim in a civil matter?

I concur in the conclusion in Part III.A of the majority opinion, that prisoners have a general First Amendment right to be present when legal mail related to a civil matter is inspected. I write separately because I don't think the majority has explained with sufficient clarity what is required to state a First Amendment claim under 42 U.S.C. 1983. I am deeply concerned that the majority opinion's characterization of Nordstrom v. Ryan , 762 F.3d 903 (9th Cir. 2014), and out-of-circuit cases which dealt with either intentional acts or pattern-and-practice allegations, Maj. Op. at 120812, may mislead the district courts and the parties into thinking

[849 F.3d 1214]