What’s popular is not always legal.

Washington state residents learned that lesson again this week after the Washington Supreme Court ruled that the Legislature does not need a two-thirds vote of approval to increase taxes.

The court said such the supermajority requirement was unconstitutional.

The state Supreme Court case was prompted by a lawsuit from the League of Education Voters, the Washington Education Association and others in a challenge to Tim Eyman’s Initiative 1053, which was approved by voters in 2010.

In their decision, the justices duly noted that the constitutionality of a supermajority requirement has “a rich litigious history,” starting with Initiative 601 in 1993.

The Legislature eventually suspended I-601 in 2005, leading to Eyman’s return with I-960 in 2007.

After I-960 was suspended, Eyman came back with I-1053 in 2010 and I-1185 in 2012 — proposals that also included the supermajority requirement for raising taxes.

This week, in a 6-3 decision, the high court finally addressed the salient issue and said that the state constitution “prohibits either the people or the Legislature from passing legislation requiring more than a simple majority for the passage of tax legislation — or any other ordinary legislation.”

While the dissenting justices raised alarm that the court majority was stepping into a “political dispute” that it had long avoided, and had abandoned “any semblance of judicial restraint,” we are heartened that the court has used this opportunity to address the long-ignored constitutional question on the supermajority requirement.