De-assisting the Blur is easy enough. Take it apart and put it back together without the torsion bar. The Blur has a ball detent. You can bend the lock bar a bit further to increase (or decrease) the strength of the detent to your preference. It's not as good of a detent as other knives that are designed as normal manual liner/frame locks, but it still works. The thumb studs are a bit awkward though; they're obviously designed to be pushed against rather than rotated. Push against the stud perpendicular to the angle and the torsion bar does the rest. But without the assist, the angle on the stud doesn't feel right through the rotation arc. It'd feel more natural if the stud was circular or conical. It still works fine, it just doesn't quite feel right.
Not all assisted Kershaws can be de-assisted. The Leek, for example, uses the torsion bar as a stop and doesn't use the detent in the closed position, so it won't want to stay closed without the torsion bar.
Frankly I don't see the need to de-assist one of these unless it's a legality issue.