Proof keeps piling up that Mayor de Blasio and his fellow progressives are not just looking to protect “otherwise law-abiding” illegal immigrants.

Last week, the city freed a gang member from Rikers, even though the feds had issued a “detainer” for him, an Immigration and Customs Enforcement official said Tuesday.

Estivan Velasquez’s criminal history includes reckless endangerment, criminal weapon possession and disorderly conduct, the feds say. In 2015, a judge ordered him deported, and ICE asked to be notified after he finished his time at Rikers.

But ICE was left in the dark because Velasquez isn’t dangerous enough for de Blasio. His offense “does not qualify as a violent or serious felony,” a mayoral aide said.

So much for that “otherwise law-abiding” talk. In any case, it’s not for de Blasio to decide whether to obey a judge’s orders and ICE detainers; snubbing federal authorities verges on aiding and abetting fugitives.

Fortunately, ICE tracked down Velasquez on its own, and he’s now in “detention pending removal.” But de Blasio’s flouting of federal law puts New Yorkers at risk — especially ICE agents and cops.

As The Post reports today, the mayor booted ICE agents from Rikers (where they’d been since 2003) after signing a new “sanctuary city” law in 2014. That leaves agents scrambling to track down illegal immigrants after release from the jail — at risk of a street confrontation if they resist arrest.

“These are known criminals who don’t want to be found,” a source told The Post. “That makes it especially dangerous and puts officer safety at risk.”

Some progressives want to do more to shield these criminals. City Councilman Rory Lancman (D-Queens) wants to change several crimes from felonies to misdemeanors in order to reduce deportation risks. Huh?

Lancman, state Sen. Jesse Hamilton (D-Brooklyn) and others also want to scrap broken-windows policing — the core of NYPD success — for fear it helps ICE.

It’s sure starting to look like “sanctuary city” means “safety last.”