"Leg lasso" can be one of the more intimidating types of guard to deal with, particularly when your partner takes a shallower hook with the lasso. It's possible for them to simply hold on and keep you in their guard, not allowing you to pass away from the lasso itself (lest you get bicep slicer-ed or swept), and there is always the threat of the omoplata and the triangle. Here is a breakdown of a simple game plan to get you started passing this dangerous type of guard, and some adjustments based on what your partner is likely to do as a counter.
Dealing with a shallow lasso hook is a bit different than dealing with a deep hook. Deep "leg lasso" implies that the person is shooting their leg straight through and up onto your back (for information on how to pass leg lasso guard, check out this previous tutorial). Fortunately, there's a very good, tried, and true system in place for passing shallow leg lasso. Start by anchoring your right hand (assuming your right hand is caught in the lasso here) as low on your partner's lapel as possible (belt will also work). Your left hand should already have inside control on the pants, as described previously. Next up, while balancing on your toes, pivot your right knee in (if you practice Muay Thai, it's just like throwing a curve knee in Thai Boxing) right at your partner's toes, effectively working to peel the lasso hook free of your arm. A word of caution: make sure not to "peel" at your partner's heel here, or else you'll end up inadvertently heel hooking your partner! Next, make a circle with your right arm, and duck your head under your partner's leg, ending up back in the middle (and making a sort of shield with your right forearm). Finally, finish what essentially amounts to an X-pass here.
After peeling the lasso hook, as an alternative, you can try passing to the side of the lasso itself. Be sure to duck your head under, as before, but this time, follow to the same side with your body, as shown in the video.
Here's another way to finish this pass:
Conclusion
The leg lasso is really just like any other type of guard: once you understand the basic mechanics, it's much easier to shut down. These passes certainly work well in conjunction with the aforementioned knee cut pass and the leg drag, and there are other far more basic options you'll want to be prepared to use in combination. As always, have fun and don't be afraid to experiment when trying out these new positions (and don't be afraid to be swept or submitted, especially if you learn something in the process!). Let me know how these work for you, too.