What does it mean to structure a tax law as an excise tax in Washington state?

Question

I read on https://www.seattletimes.com/seattle-news/politics/lawsuit-against-washingtons-new-capital-gains-tax-can-move-forward-judge-rules/

Democratic lawmakers have said they structured the new law [on long-term capital gains] as an excise tax".

What does it mean to structure a tax law as an excise tax in Washington state?

Answer 1

In this context, structuring a capital gains tax as an excise tax means that the taxation of capital gains on a stand alone basis is divorced from the context of a larger comprehensive law taxing income in general (which Washington States's constitution prohibits).