As Federal Communications Commission Chairman Ajit Pai prepares to begin the repeal of net neutrality rules, a resistance to his efforts has already started. Senators Edward J. Markey (D-Mass.), Richard Blumenthal (D-Conn.) and Ron Wyden (D-Ore.) led a call Wednesday to begin laying the groundwork for a legislative effort to protect net neutrality.

The senators, along with leaders from open internet advocacy groups Free Press and Fight for the Future, made clear their intention to protect not just the principles of net neutrality, which requires all data to be treated as equal, but also the legal means of enforcing those principles.

“We’re not just going to sit ideally by and deliver the internet to the big cable companies,” Sen. Wyden said.

Read: at Is Net Neutrality? How FCC's Title II and Open Internet Rules Came To Be

At stake are the President Barack Obama-era protections passed by the FCC that reclassified the internet as a common carrier under Title II of the Telecommunications Act. That classification, established by the Open Internet Order, gave the FCC the regulatory power to protect net neutrality principles, which prohibit internet service providers from blocking, throttling or prioritizing any data.

Evan Greer, the campaign director of Fight for the Future, described net neutrality as the “first amendment of the internet.”

Ajit Pai, the FCC chairman appointed by President Donald Trump, has stated his intention to undo those protections. While Pai is expected to present his replacement plan in full Wednesday, early indications suggest he will propose doing away with the common carrier classification and will ask internet service providers to voluntarily agree to net neutrality principles instead of having legal recourse for enforcing the rules.

Sen. Markey said the idea of supporting an open internet but not supporting net neutrality is “like saying you value democracy but don’t see a need for a constitution, or you like math but you don’t like numbers.”

Read: Is Net Neutrality Dead? What The Internet Will Look Like Without Open Internet Rules, Title II

The group of Democratic senators began laying out what forms opposition to Pai’s changes may take, including mobilizing the public and mounting legal challenges. A point of emphasis for the group was harnessing support from the business community, where there is considerable support for net neutrality principles.

Sen. Markey said he has already spoken with internet companies like Carbonite, TripAdvisor and Wayfair and believes “net neutrality is an essential element” for companies that do most of their business online.

“What’s at stake here is not only consumer convenience and enjoyment but literally jobs and economic success,” Sen. Blumenthal said, noting that about 800 U.S. businesses have already written to the FCC to voice opposition to changes to net neutrality.

Opponents to the Title II protection of net neutrality have often argued the common carrier classification has slowed investment in internet infrastructure and stifled innovation from internet service providers.

Craig Aaron, the President and CEO of Free Press, said that is not the case. ISPs have continued to expand their networks, with overall investment up five percent since net neutrality was put in place, and many companies have begun working on next generation networks in that time.

While the senators and open internet advocates promised a unified front against changes to net neutrality, they also made it clear that overturning the current set of rules won’t be as easy as one might imagine.

Republicans in the Senate and Congress were able to repeal the Broadband Consumer Privacy Rules, which would have prevented ISPs from collecting user data without permission, because they acted quickly and used legislative power. The fight for net neutrality will not be subject to the same kind of expedited process.

In order to undo the Title II classification, chairman Pai will have to put together a proposal for a hearing. That could happen as soon as May. But to overturn the rules, the commission will have to present a docket that shows something significant has changed since the Open Internet Order was passed.

“There is no such fact based docket now,” Sen. Blumenthal said. “Any effort to roll back [net neutrality] in draconian fashion could be against the law.”

Even if the legal burden presents a challenge to chairman Pai, the Senators emphasized that the most powerful tool for protecting net neutrality will continue to be the voice of citizens, just as it was in passing the rules in the first place.

More than four million people wrote to the FCC in 2015 to support net neutrality, and a similar outcry is expected to any attempt to upheave the rules. Sen. Blumenthal said the first step to protecting net neutrality is to “mobilize and galvanize the seismic outrage that should follow this kind of misguided effort.”

While the earlier defeat on broadband privacy rules may seem discouraging for just how much of an impact public sentiment has on the Republican voting bloc, Sen. Markey said he believed with more time, they could have won that vote.

“I think if we had a revote on [broadband] privacy, we would win right now,” he said. “Many Republicans are now understanding how passionate Americans are about these issues.”

The fight for net neutrality will be longer, and much more public than the vote on broadband privacy. The Senators and advocates believe that will play to their advantage.

“This is not something they can sneak through,” Aaron said. “They will have to have this fight in the light of day”