From the PANYNJ web site:
"The Port Authority reserves the right to restrict videotaping and photography at its airports. Videotaping in runway and taxiway areas at all airports is prohibited at all times. Videotaping and photographing at security checkpoint areas operated by the U.S. Transportation Security Administration is prohibited without the consent of the TSA
The IKEA lot is private property, so they can restrict photography there all they want. Most of the rest of EWR
is completely hemmed in by development, so again private property. There are a few street locations, but they're mediocre at best with tons of overhead wires and you'll still be run off if the cops see you. EWR
has some interesting traffic, but it's not really much fun to take pictures there.
Oh, and speaking of the parking lot len90 referenced, if you lay low you can get shots until someone sees you, but it costs something like $18 to park there even if you're only there for 15 minutes.