Today, the FCC’s Restoring Internet Freedom Order takes effect, effectively repealing net neutrality protections in the US. The effects probably won’t be sudden; we’ve explained what might happen without the rules and what’s already happened since the vote last year. But no matter what happens this week, repeal opens the door to some real abuses of internet service providers’ power — not hypothetical scenarios, but real predatory practices we’ve already seen in the past.

These incidents show how complicated the issue of net neutrality is: all of these transgressions happened after the 2005 Internet Policy Statement, which laid out four “open internet” principles that would guide the agency’s decisions. Some happened during periods where firm rules were standing, others during periods when they’d been struck down. Companies reconsidered their choices because of public outcry, official investigations, and practical changes in technology. So while today is a disappointing day for net neutrality, keeping internet companies in check isn’t just about having the right rules in place. It’s about having regulators and an American public that will make trouble for anybody breaking them.

Comcast blocks peer-to-peer networks

In 2007, America’s second-largest internet service provider was caught injecting its own commands into users’ internet traffic, stalling peer-to-peer applications like BitTorrent and Gnutella. Comcast wasn’t outright blocking these tools, but it was making them basically unusable. Comcast said it had to throttle peer-to-peer data to manage network quality, and since the services were often tied to piracy, it had picked an easy target. Even so, criticism was fierce. Comcast reached an agreement with BitTorrent to end the practice, and soon after, the FCC found that Comcast had violated the Internet Policy Statement, an early and less binding version of net neutrality rules.

This was a potentially precedent-setting move, but a court ruled that the FCC didn’t have the authority to censure Comcast, overturning the decision. The case led Obama’s first FCC chair Julius Genachowski to push for a more formal net Open Internet Order neutrality framework, which passed in 2010. (This order was itself overturned in 2014, until Genachowski’s successor Tom Wheeler replaced it a year later.) Even if current FCC chair Ajit Pai has downplayed its importance, Comcast’s throttling misadventure remains perhaps the best-known — and most egregious — example of how companies could exploit weak net neutrality rules.

AT&T blocks Skype

When Voice over Internet Protocol (VoIP) apps started rapidly gaining popularity in the ‘00s, telecommunications companies worldwide blocked them at every turn. Smartphones made these services more attractive than ever, which potentially threatened traditional mobile calling plans. So when Skype came to iOS in April 2009, AT&T (which held an exclusive contract for the iPhone) convinced Apple to block calls made over its wireless network.

AT&T policy executive Jim Cicconi was straightforward about the company’s reasons. “We absolutely expect our vendors ... not to facilitate the services of our competitors,” he said. “Skype is a competitor, just like Verizon or Sprint or T-Mobile.” But once FCC chair Genachowski was confirmed later that year, the FCC took Apple to task for blocking Google Voice on iOS — which put the issue in the spotlight and prompted AT&T to take a “fresh look” at the VoIP ban. It ended up reversing the policy a few months later.

Verizon protects Isis and blocks Google Wallet

AT&T, T-Mobile, and Verizon announced a mobile payment system called Isis in 2010, but before it had a chance to launch, Google announced its own Google Wallet payment app for Android. Google tried to add Wallet to Samsung Galaxy Nexus phones on Verizon, but Verizon reportedly nixed the plan; publicly, it claimed the system wasn’t compatible with the Galaxy Nexus NFC chip.

Net neutrality rules were actually in place by 2011 when this happened. But Google Wallet was in a complicated position. Verizon wasn’t exactly blocking web traffic; it was refusing access to a feature of the phone. (Also, ironically, Google and Verizon had jointly pushed to weaken mobile broadband protections.) Stanford University internet law professor Barbara van Schewick still asked the FCC to investigate, but Verizon successfully avoided supporting Wallet until Isis launched in 2013. Isis didn’t stick around for long, though, even after rebranding as Softcard to avoid associations with the Islamic State. Google acquired its technology in 2015, and the service shut down not long after.

MetroPCS blocks everything but YouTube

Just a month after the Open Internet Order passed, MetroPCS launched a discount phone plan that seemed to violate its spirit. The $40 plan offered unlimited talking, texting, and web browsing. But if you wanted to stream audio or video, your only option was YouTube, unless you paid extra for “additional data access.” Net neutrality advocates urged the FCC to investigate, and MetroPCS responded by filing a lawsuit against the agency, hoping to get the new rules overturned.

MetroPCS argued that it wasn’t trying to unfairly privilege any particular company. It had simply found that customers expected YouTube as part of their service, and it had developed a way to support YouTube on its extremely limited wireless spectrum while offering the option to get other services for a higher price. But regardless of intent, it was locking customers into specific web platforms, which was exactly what net neutrality advocates wanted to prevent.

In the end, the plan didn’t even last through the end of the year, because MetroPCS stopped carrying the only phone that supported it. And T-Mobile dropped the FCC lawsuit when it acquired the company, signaling that it wasn’t interested in continuing the battle MetroPCS had started. When T-Mobile started pushing a walled app garden with the Binge On program, it did so by making certain services cheaper and easier to use, not by dropping support for everything else. It was a much friendlier-sounding way of pushing the boundaries of net neutrality — which, now that public opinion is the main barrier to violating net neutrality, is something we’ll probably see much more of in the future.