Texas can however make it illegal to have drugs in your system while in Texas
I’m not sure that’s actually a crime in Texas (please link a law if you know of one), and using it as evidence of prior drug possession is legally iffy as this Ohio case shows. In your example of consuming cannabis in California before traveling to Texas, it would be an even more difficult case for Texas prosecutors.
I don’t want the parole thing to confuse the issue
It does though; parole can include restrictions like “pass random drug tests”, “don’t drink alcohol”, etc… that can’t be imposed on people without a prior criminal conviction. It’s probably best to leave parole out of the discussion entirely.
the concern is ipso facto the termination.
When it comes to an abortion outside the state, the laws I’m aware of concern travel for the purpose of abortion. An alternate purpose for the travel could be useful as a defense, but that’s best delivered by one’s lawyer after charges are filed.