Too lazy to call someone who would know, so gonna ask here instead.

Parent with custody lives in Texas, and other parent lives in Kansas.

Child is 17 and will be 18 in March.

Child "runs away" from parent in Texas to live with parent in Kansas.

What can parent in Texas do about it? 

That is tricky. I just googled it and it looks like a teenager can move out at the age of 17 without parental consent in Texas. Since she is a Texas resident I would assume that Texas law would rule, but I could be wrong. This is a great question for a civilian lawyer in both states. 

Sounds promising. I figured it would be kind of tricky, but in a good way for my side. :) Hes practically an adult. 

Hi that is tricky , I'm from Texas and at age 17 the child can leave . I know this may not help but it true. 

If you are paying child support you may still be liable for it until you get the courts to change it. 

Yeah, not worried about the child support part. Easier and cheaper to just let it run itself out than to bother having it changed last minute like this. I mean March is really just around the corner.