Inslee said the new measure would protect an open internet in Washington, which he described as having "allowed the free flow of information and ideas in one of the greatest demonstrations of free speech in our history".
At least 25 other states are considering net neutrality bills, including California, Illinois, and NY.
The law will prevent internet service providers from implementing paid prioritization, throttling traffic or blocking certain content. The dismantling of the nationwide rules, approved by the Federal Communications Commission past year, set off a fierce outcry from consumers and tech companies.
In an official rebuke of the Federal Communications Commission's decision to repeal net neutrality on the federal level, Washington Gov. Jay Inslee signed the nation's first state law to protect the policy.
Provisions of the law could be prosecuted under the state's Consumer Protection Act.
The repeal, supported by FCC Chairman Ajit Pai and the major cable and telecom companies and opposed by large and small tech Internet companies, garnered intense public interest.
The bill prohibits internet providers in Washington from blocking content, services and devices, with a few exceptions.
Inslee said he's confident the states are within their rights to regulate internet service even though the FCC says no.
"This is not a partisan issue", Norma Smith, a Republican who co-sponsored the bill in the House, said in a statement last month.
The state governments of New York, Montana, New Jersey, Vermont, California and Hawaii have sought to counteract the FCC deregulation with executive orders that set net neutrality principles for contracting of internet service, similar to Oregon's approach. Members of Congress have also made noises about reimposing federal net neutrality rules, but their efforts are not moving very fast. It's likely ISPs will sue Washington state to find out if that works.
Washington's elected officials are right to challenge the Federal Communications Commission's awful decision to rescind net-neutrality protections. The F.C.C. said it got rid of the rules because they restrained broadband providers like Verizon and Comcast from experimenting with new business models and investing in new technologies.