I've never seen a Canon lens with any kind of adhesive holding a rubber focus ring on. The rubber should be "stretchy" enough that it will contract around the metal focus ring underneath it.

Some Canon lenses do have tape under the rubber focus or zoom rings, but it is not double-sided and it is not there to hold the rubber rings in place. It's there to cover access holes for adjustment and/or disassembly to give the lens more resistance to dust and weather. You're just as likely to see the same kind of tape covering holes on an inner barrel that is inside an outer barrel held to the rest of the lens by several screws.¹

If the rubber focus or zoom ring on a lens has gotten stretched or been exposed to chemicals that reduced its elasticity, the best thing to do is replace it with a new rubber ring. I would avoid gluing anything if the metal focus ring underneath the rubber ring has any access holes or screws in it. Some of Canon's L lenses don't, but many do.

The EF 28-35mm f/2.8 L has two (different) screws holding two bushings (Canon calls them "zooming collars") in holes underneath the rubber on either side of the metal zoom ring. I wouldn't recommend using any kind of adhesive there as the adhesive may well get in the holes and defeat the purpose of the bushings, which is to make the motion of the zoom ring smooth. There do not appear to be any access holes on the focus ring of the EF 28-35mm f/2.8 L, but there's always the danger that adhesive could make its way into the gaps between the focusing ring and the lens barrel behind the focusing ring and between the focusing ring and the front cover in front of the focusing ring.

¹ To see an example of the latter, scroll about 3/4 of the way down at Roger Cicala's lensrentals blog A Few Easy Lens Dustings. There's a photo of Aaron pulling such a piece of tape off the inner barrel of an EF 70-200mm f/2.8 L.