WHEN FEDERAL Communications Commission Chairman Tom Wheeler announced Feb. 4 that he would propose rules to ensure that the Internet remains open for all users, advocates of net neutrality were ecstatic.

Net neutrality is the principle that Internet service providers should treat all Web traffic the same and not block or slow certain data streams. (Comcast, Verizon and AT&T are among the biggest ISPs.)

The five-member FCC is poised to formally adopt new rules tomorrow in Washington, and Wheeler likely has the votes to pass his plan. In sum, the plan would use FCC authority under Title II of the Communications Act and reclassify retail broadband as a public utility - like rules applied in the 20th century for telephone networks.

The big question, then, is: What happens next?

The ISPs will probably sue over the new rules. Republicans in Congress are huffing and puffing about higher taxes, less consumer choice and alleged interference by President Obama, and are not ruling out holding hearings. (In November, Obama called for prohibiting ISPs from creating "fast lanes" and "slow lanes" for different content.)

The ISPs twice have persuaded the courts to overturn FCC open-Internet orders, but "this time the FCC is using a different legal theory," said Kevin Werbach, an associate professor at the University of Pennsylvania's Wharton School and a former FCC official.

He said the Title II theory that Wheeler has endorsed puts the FCC on stronger legal ground but also may open up new challenges. "The lawsuits aren't likely to be heard until next year, although the ISPs may well ask the court to stay [new] rules while the lawsuit is pending," Werbach said.

But for that to happen, "the court has to find that [ISPs] have a substantial likelihood of success on the merits, so that's an unlikely step but not an inconceivable one," Werbach said.

Meanwhile, ISPs and their supporters are rallying around legislation proposed by Republicans that would mandate nondiscrimination rules but would prohibit the FCC from imposing Title II regulation or any further rules. God forbid a regulatory body should actually regulate.

Of course, almost everyone - even conservative Republicans - opposes unreasonable discrimination and favors an open Internet. But that's hardly reassuring.

Finally, an open Internet is especially critical for startups and small businesses. The FCC's Title II reclassification will, among other things, allow it to investigate and address complaints - which could come from small businesses - that ISPs are violating nondiscrimination rules.

"Small businesses and startups don't have the same leverage to pressure ISPs to change their practices as larger companies . . . so the ability to appeal to the FCC is particularly valuable," Werbach said.

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