Jamming civilian GPS

The new Phrack has an interesting piece on GPS jamming. I'm no radio engineer, but this seems pretty plausible to me. When civilian GPS got its accuracy bump a couple years back, I remember reading a lot of reports that the military could selectively jam GPS, so that their opponents wouldn't get positional data, but US troops would. This is part of the premise of a story I finished rewriting the other day, about Open Spectrum guerrillas:

Lee-Daniel went out with a crew that Elaine was leading, up on the northern border of the sovereign. She had two junior surveyors with her, all of them loaded with positioning gear that tied into Galileo, the European GPS network — the Galileo gear cost a fortune, but they'd found that their American GPS kit often mysteriously stopped working when they were working on projects in the territorial USA. They'd ordered the Euro stuff from a bunch of anti-globalization activists who'd found that the same thing happened in any city hosting an economic summit. Europeans were more likely to treat infrastructure as sacrosanct, while the US was only too happy to monkey with GPS for tactical reasons. The Series A man hated the expense of the Galileo gear, hated paying off crusty-punk Starbucks-smashers for critical tools, hated the optics of looking like a bunch of anarchists instead of a spunky startup.

Seems a little more plausible in light of this:

A low cost device to temporarily disable the reception of the civilian
course acquisition (C/A) code used for the standard positioning service
(SPS)[1] on the Global Positioning System (GPS/NAVSTAR) L1 frequency of
1575.42 MHz.

This is accomplished by transmitting a narrowband Gaussian noise signal,
with a deviation of +/- 1.023 MHz, on the L1 GPS frequency itself. This
technique is a little more complicated than a simple continuous wave (CW)
jammer, but tends to be more effective (i.e. harder to filter) against
spread spectrum based radio receivers.

This device will have no effect on the precise positioning service (PPS)
which is transmitted on the GPS L2 frequency of 1227.6 MHz and little
effect on the P-code which is also carried on the L1 frequency. There may
be a problem if your particular GPS receiver needs to acquire the P(Y)-code
through the C/A-code before proper operation.

This device will also not work against the new upcoming GPS L5 frequency
of 1176.45 MHz or the Russian GLONASS or European Galileo systems. It can
be adapted to jam the new civilian C/A-code signal which is going to also
be transmitted on the GPS L2 frequency.