So Israelis committing an offense abroad should be judged under international law?
You're delusional. They are judged in the same country in which the commit the offense.
Which is the exact situation here.
The Fourth Geneva Convention is a treaty Israel is a signatory too, as well as others that prescribe lawful procedures to try members of an occupied population for crimes, as well as generally prescrbing what proper judicial process is. There are some basic human rights all have under these treaties.
One provision is The Fourth Geneva Convention says an occupied population cannot be imprisoned outside of the occupied territories. Israel so egregiously violates this provision, I expect it qualifies as a grave violation of the convention and constitutes a war crime. Each detention inside Israel of a Palestinian from East Jerusalem or the WB or Gaza is a war crime.
The other serious matter is Palestinians do not get fair trials, the entire process from detention to conviction to sentencing to incarceration violates rights Palestinians have under intl law. We have torture documented for decades, the practice of using torture to coerce false confessions, administrative detentions that violate intl law, kangaroo military courts, denial of medical care in prisons, attacks on prisoners in prisons, unlawful solitary confinement, etc