I hope you don't find my advice annoying, but the best way to defend a good leg rider is not let him get the legs in to begin with. Stand up, stand up, stand up. Explode up on the whistle and never stop hand fighting and positioning the hips to create space. If you get brought back to the mat, immediately get back to your feet.

From my outline and by no means a complete list of counters:

COUNTERS TO THE CROSSBODY RIDE

Catch the leg
? Catch the leg from the inside with the same side arm just as he is putting it in.
? Sitout toward the leg and drop to the opposite shoulder.
? Turn in, throw the leg up to the ceiling and come out the back door.

Mule kick
? Kick your foot back and high as the leg comes in.
? Sitout and turn in for an escape.

Hip smash
? Reach back with your inside arm and grab his hip.
? Pull him off you, extend your leg, and smash your inside hip to the mat.
? Sitout and turn for an escape.

Granby roll
? Tripod and cross your inside foot in front of your outside foot.
? Roll across your shoulders and kick your leg out.
? Turn and face opponent.

Wrist and scoot (this is my favorite because you end up in a cross body ride and because as far as I know, I invented it)
? Reach across your chest with your inside hand, and grab opponent’s near wrist (the one closest to your head). This can usually be done if he’s “fishing” for a guillotine.
? Pull his arm across your chest and sit into him.
? Scoot your hips away to create space, and come up in your own cross body ride.

Grab foot
? Reach into your crotch with your far arm and grab his foot.
? Pull it out and across your waist.
? Drop your inside hip to the mat and get a whizzer.

Hip rotator
? Lift your outside knee and rotate your hips into your opponent, causing him to bring his back leg up toward your head. Do not let him apply the split scissors.
? Reach back, grab the ankle of his bracing leg and sit into it.
? Keep your head up and come around for a reversal

If you know the leg is coming and don't think you can beat him to the first move just wait and catch it... then clear it over your head and do an extended sit to separate yourself.

If he grabs his foot or secures around you jam your elbow into his shin and push the leg out away from your body. Hold his foot with both hands and jam the elbow into the shin while you crank the foot toward you and push the elbow away from your body.. after it starts to hurt him you can clear the leg more easily because he will be moving in the direction your elbow is pushing.