Odd...
The odd thing is that while it is mentioned in Part 97, it's not in 97.301 which sets out the frequency allocations for the different license classes. Instead, it's in 97.401, "Operation during a disaster."
97.401(c): A station in, or within 92.6 km of, Alaska may transmit emissions J3E and R3E on the channel at 5.1675 MHz for emergency communications. The channel must be shared with stations licensed in the Alaska-private fixed service. The transmitter power must not exceed 150 W.
It used to be on the ARRL bandplan chart but they seem to have dropped it. Not sure why.