SEATTLE — A frequent ballot initiative promoter sued Washington state on Monday over the constitutionally suspect way lawmakers voted to make it easier to prosecute police for negligent shootings.

Tim Eyman filed the lawsuit in Thurston County Superior Court four days after lawmakers approved and Gov. Jay Inslee signed a compromise measure backed by both activists and law enforcement groups.

The agreement is intended to end years of wrangling over an existing state law that made it nearly impossible to hold officers criminally liable.

Amid outrage over questionable police shootings, the organization De-escalate Washington gathered nearly 360,000 signatures for an initiative to the Legislature to change the law by eliminating a requirement that prosecutors prove an officer acted with malice.

Under the state Constitution, lawmakers can approve such measures as written; reject or ignore them, in which case they appear on the November ballot; or propose an alternative to appear alongside the original on the ballot.

In this case, the Legislature crafted a fourth option: It passed the original — Initiative 940 — as well as a law to amend it with changes called for by police groups and supported by activists.

Mindful of the Constitution’s requirements for a public vote, however, lawmakers also said the law to amend the initiative would only take effect if no referendum is filed by June to challenge it.

Eyman argued that if it’s allowed to stand, the Legislature’s move would effectively abolish the people’s right to petition the Legislature by initiative. Voters could collect signatures for a measure, only to see lawmakers drastically change it. Voters would then have to collect more signatures if they want to challenge the Legislature’s version by referendum.

Eyman has promoted about 20 initiatives over the years, many of them aimed at limiting taxes. He asked the court to order Secretary of State Kim Wyman to place both the original Initiative 940 and the amendment, House Bill 3003, on the fall ballot. The case is titled Eyman v. Wyman; a hearing is set for April 20.

“The Legislature went rogue, disrespecting the initiative petition signers and preventing voters from exercising their right to vote,” Eyman said in the lawsuit.

Sen. Jamie Pedersen, a Seattle Democrat who supported the measure, said Monday he disagreed that the process threatened the people’s right to propose initiatives to the Legislature. As a practical matter, he said, the Legislature could only act the way it did if an initiative’s sponsors supported the changes; otherwise, there would be a public outcry.

Furthermore, he said, once the Legislature passes an initiative as written and it takes effect, lawmakers can amend it in the normal manner — unlike an initiative directly to the people, which can’t be amended for two years without a two-thirds supermajority.

“We could have called a special session in June and amended I-940 after it went into effect,” Pedersen said. “Can we do it with contingency legislation? I think we should be able to, but it’s fair to say that’s a novel question.”

In 1971, the attorney general’s office issued a legal opinion saying that anytime the Legislature made changes to an initiative proposed to it by the people, those changes must appear alongside the original on the ballot. The opinion also said the Legislature couldn’t simply pass a separate law altering the initiative, even to make simple corrections.

The constitutional concerns were aired during the rush to pass the deadly force compromise before the legislative session ended last Thursday. It passed with support from both parties in the House and from majority Democrats in the Senate.

Republican Sen. Mike Padden, of Spokane Valley, and others said they supported the underlying bill and were pleased the sides had compromised. But they described the process as an effort to ensure the Constitution didn’t get in the way of good policy.

“I have incredibly grave concerns that we are creating a convoluted process for getting around a constitutional right,” said Sen. Joe Fain, R-Auburn.

Attorney General Bob Ferguson’s office said before the vote that it would defend the Legislature’s action in court if necessary. In an email, spokeswoman Brionna Aho said the office would not discuss its analysis of whether it was constitutional.

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