I think winter fishing by members of the Algonquins of Ontario was a legal grey area for a long time, in practice they did it without enforced restriction because no one wanted another legal case to complicate the Algonquin land claim (as per Rory's comments quoted by John above). Finally, as part of the agreement in principle, the parties established "interim winter fishing measures". Under these measures, the Algonquins are allowed to fish in the winter in much of the park, but not in certain areas: the Dickson-Lavielle system, the Galipo River system, the Hogan-La Muir chain, and the Coldspring area in the park's northwest. In addition to staying off these lakes in the winter, the Algonquins accept a spawning season closure on lake and brook trout throughout the park, and must abide by the live baitfish ban and the six year-round sanctuary lakes. This was discussed on the old forum here.
I'm not 100% sure of the current legal status of these interim measures.