I read that
The United States Constitution and forty-three state constitutions include a Speech or Debate Clause granting legislators a legal privilege for their legislative work.
Which US state constitutions don't have such an explicit legislative/parliamentary privilege?
And if it's not too much to also ask here: is there a common enough reason among these states why they don't have this privilege in their constitutions?
The linked article in the original article relies for this assertion on Steven F. Huefner, "The Neglected Value of the Legislative Privilege in State Legislatures", 45 WM. & MARY L. REV. 221, 221 (2003). This article provides a state by state summary in an appendix starting at page 308 of that volume of the law review. See also pages 235-237 summarizing that data.
The states with no state constitutional speech and debate provision as of 2003 were: California, Florida, Iowa, Mississippi, Nevada, North Carolina and South Carolina. But, all of those states protect some of the things protected by such a constitutional provision either as a matter of case law or a state statute, so the distinction is really mostly one of style rather than substance and is mostly due to historical accident. The situation in those seven states is summarized in footnote 54 at pages 237-238 of the 2003 article:
The seven states are California, Florida, Iowa, Mississippi, Nevada, North Carolina, and South Carolina. All but two of these states- North Carolina and Florida- have a constitutional provision privileging its state legislators from certain types of arrest or civil process during the time the legislature is in session. Florida once had both a Speech or Debate provision and an arrest provision in its Constitution, but it has not had either provision since 1868. See Girardeau v. State, 403 So. 2d 513, 515 n.3 (Fla. Dist. Ct. App. 1981). Some interpreters occasionally have used these arrest provisions also to support the recognition of a common-law privilege of free legislative debate. See, e.g., 1979-80 Op. Att'y Gen. Iowa 173, available at 1979 Iowa AG LEXIS 101 (using constitutional arrest privilege and limited statutory Speech or Debate privilege to derive broad common-law legislative privilege) [hereinafter Op. Att'y Gen. Iowa]. Such a privilege, however, likely exists even in states without a constitutional arrest clause. For example, the Florida Supreme Court in dicta has strongly signaled its readiness to recognize a legislative privilege as a matter of common-law in appropriate cases. See Hauser v. Urchisin, 231 So. 2d 6 (Fla. 1970); see also Girardeau, 403 So. 2d at 516-17. In California, state courts apparently have recognized a common-law legislative privilege for state legislators, following the U.S. Supreme Court in Tenney v. Brandhove. See Allen v. Superior Court, 340 P.2d 1030, 1034 (Cal. Dist. Ct. App. 1959). But cf Hancock v. Burns, 323 P.2d 456,461 (Cal. Dist. Ct. App. 1958) (noting that inflicting bodily injury at a hearing would not be privileged). Although Mississippi does not yet appear to have expressly recognized a legislative privilege for state legislators, it was one of the earliest jurisdictions to recognize a common-law privilege for local legislators. See Jones v. Loving, 55 Miss. 109, 109 (1877). North Carolina also has recognized a common-law legislative immunity for local legislators. See Stephenson v. Town of Garner, 524 S.E.2d 608, 612-13 (N.C. Ct. App. 2000); Vereen v. Holden, 468 S.E.2d 471, 473-74 (N.C. Ct. App. 1996). Meanwhile, North Carolina and Iowa have statutory privileges. The North Carolina statutory provision closely tracks the federal and typical state constitutional provisions, stating that state legislators "shall have freedom of speech and debate ... and shall not be liable to impeachment or question, in any court or place out of the General Assembly, for words therein spoken." N.C. GEN. STAT. § 120-9 (2001). In contrast, Iowa's statutory provision expressly provides only that state legislators "shall not be held for slander or libel in any court for words used in any speech or debate in either house or at any session of a standing committee." IOWA CODE § 2.17 (2002). The Iowa attorney general has opined, however, that at common law state legislators should receive the same broad immunity as provided by the U.S. Constitution's Speech or Debate Clause. See Op. Att'y Gen. Iowa, supra. Some states with constitutional legislative immunity provisions also have statutory immunity provisions. See, e.g., MICH. COMP. LAWS ANN. § 4.551 (West 1994). The District of Columbia also has a statutory provision granting its legislative council a privilege analogous to that provided by the federal Speech or Debate Clause. See D.C. CODE ANN. § 1-301.42 (2001).
As a partial answer (found later in the same source), Florida is one such state without an explicit provision. On the other hand, Florida's supreme court has concluded that there is an implicit equivalent privilege granted by their constitution's separation of powers clause. However they also found that this [implied] privilege is not absolute, i.e. that it may yield “compelling, competing” interest, e.g. one found in another constitutional provision:
In League of Women Voters of Florida v. Florida House of Representatives, the Supreme Court of Florida held that the legislative privilege must yield to a competing state constitutional prohibition against partisan gerrymandering. Unlike Virginia and Rhode Island, Florida does not have a Speech or Debate Clause in its state constitution. Nevertheless, the Florida Supreme Court held in League of Women Voters that state legislators and legislative staff members possess a legislative privilege under the Florida Constitution’s separation of powers provision. Despite this finding, legislators were deemed unprotected by the evidentiary privilege in the redistricting context due to a competing constitutional provision against partisan gerrymandering. [...]
The court first held that a legislative privilege exists in Florida based on the principle of separation of powers found in Article II, section 3, of the Florida Constitution. The court reasoned that although Florida has a strong public policy favoring transparency and public access to the legislative process, that policy is outweighed by the crucial role that the separation of powers principle plays in the state government. Second, the court held that the legislative privilege in Florida was not absolute and may yield to a “compelling, competing” interest. In so holding, the court employed a balancing test similar to the one used in United States v. Gillock, but balanced competing state, instead of federal, interests.