Quoted:
If you mean the barrel block the rear sight is mounted on, yes they can be canted.

First step is to make sure it's the sight block and not the entire barrel that's installed off center.
This is done by just looking at the front sight and gas block, then checking the spacing of the upper and lower hand guards.  A bigger gap on one side of the front of the hand guards may indicate a rotated barrel.

Assuming it's the rear sight block that's canted, the "fix" is to drive out the sight block pins or pin and use a soft hammer to bump the block over until it's straight.
It's best to remove the actual sight before doing this.
Removal of the AK rear sight is in itself a PITA.  You have to press down on the front of the strong spring under the front of the sight while pressing down on the front of the sight and sliding it backward out of the sight block.
Note that the "pin" in the front of the sight is NOT a pin, those are lugs machined on the sight.  They don't drive out.

Note that barrel parts are pressed on and are TIGHT so they never come loose.  The pins are just insurance.
Parts like the rear sight block can be very resistant to moving ,so be careful not to bend or distort the block.
When bumping it over, you may be best to use a hardwood block and a dead blow hammer to prevent damaging it.

After the block is straight, you carefully use a drill to re-cut the grooves in the barrel the pins fit in and drive in pins.
If you over-size the holes you can make larger pins from drill rod or use taper pins similar to those used on AR-15 front sights.

When re-drilling the grooves in the barrel, remember...... The intent is to cut new grooves in the barrel, NOT drill out and enlarge the holes in the sight block.

Quoted:
Man, why do people who don't have a clue about AK's get good deals on rare rifles?