The Sullivan Break Away S-hook that you find on the
Supply Line does release at 280 pounds, which should make it legal in your state. As for fastening it to the lock, just open one eye of the hook slightly, and pass it through the hole on the lock where you would ordinarily fasten the end ferrule. Then use the other eye of the BAS to accommodate the cable and end ferrule.
How the hook hangs off the lock, will determine how you bend the end of the cable to get the loop round. On, for example, a cam lock, the flat part of the s-hook is facing the cable. Bend the end of the cable directly away from the memory curve to get the desired results. On a washer type lock, the flat part of the s-hook will not be facing the cable, but will be in line with it. Here, bend the end of the cable at 90 degrees to the memory curve. This may look funny at first, but I assure you it will make the lock function better.
Here's a couple of pictures that will help:
Personally, I recommend that you use these on snares that (including extensions) are not much longer than five or six feet. A longer snare, particularly in a non-entanglement situation, can give the animal a running lunge and may allow an animal like a coyote to pop the s-hook open. Shorter snares lessen the impact on a lunge.
For those who are interested, the release pressure on a break away device is determined by a "static" test. In other words, it's how much dead weight the snare will lift before the device gives up. A running lunge obviously generates more energy than this.
Here's a link that will take you directly to the Break Away S-hook page.
Sullivan Break Away S-hook -- Hal