Another way is a plate that bolts between the springs and axle.
Saskatchewan Motor Vehicle code says you can't weld on the springs. It says nothing about axle tubes and shock mounts because that's how they do them from the factory.
Suspension system
21(1)
The suspension system of the vehicle shall:
(a) in the case of a two axle vehicle, distribute the weight of the vehicle and
its load so that no more than 75% of the total weight is carried on one axle;
(b) not have broken or welded leaf or coil springs;
(c) not have loose, bent, cracked, broken or disconnected U-bolts, centre
bolts, mounting shackles, stabilizers, radius rods or equalizers; and
(d) have a bump pad or other secondary device that prevents the frame or
body from contacting the tire or wheel in the event of failure of any component
of the primary suspension system.
(2)
In the case of a type A-1 vehicle, the suspension system shall:
(a) prevent any part of the vehicle other than the tires from contacting the
ground when one tire is flat;
(b) have spring shackles that are not longer than those specified by the
vehicle manufacturer; and
(c) have at least one functional damping device or shock absorber for each wheel.