Permission denied when trying to edit/create acpi thermal trip points

Trying to edit an acpi thermal trip point from /sys/class/thermal/thermal_zone0:

$ echo 75000 > trip_point_1_temp
bash: trip_point_1_temp: Permission denied

I get the same result using sudo.

I also tried with the same result:

$ echo 75000 | sudo tee trip_point_1_temp
and
$ sudo sh -c "echo 75000 > trip_point_1_temp"

I also tried "echo -n" instead of just "echo" with the same result.

I also tried echo "75000" instead of just echo 75000.

I also tried the above commands from /sys/devices/virtual/thermal/thermal_zone0 (where the links from /sys/class/thermal point), all with the same result.

These thermal attributes are supposed to be editable by the user, and this is confirmed byhttp://www.kernel.org/doc/Documentation/thermal/x86_pkg_temperature_thermal

I have read that there was one or more kernel bugs in the past that behaved this way. Is this a bug, or is there a proper way to edit/create/save these thermal attributes?

This is under Lubuntu 14.04 32-bit desktop version, with kernel 3.13.0-27.50-generic. But I get the same results going back to Lubuntu 12.04, also with Kubuntu and Ubuntu.