that's the only thing I can think of, instead "...capable of edveloment.." what you want to avoid

1. Der Embryo als solcher wird nicht definiert, verwendet wird jedoch der Begriff "entwicklungsfähige Zellen", mit dem die befruchteten Eizellen und die Zellen, die sich daraus entwickeln, bezeichnet werden.

2. Solche pluripotenten embryonalen Stammzellen können mit Hilfe von drei Methoden zugänglich
gemacht werden: Sie können aus Blastozysten(21) stammen, die durch in-vitro-Fertilisation gewonnen wurden (Embryonic Stem Cells = ESC). Sie können aus primordialen Keimzellen
(Embryonic Germ Cells = EGC)(22) entwickelt werden. Sie können als individualspezifische
embryonale Stammzellen durch Zelltransfer in entkernte Einzellen - nach der Dolly-Methode -
gewonnen werden

I cring a bit writig this, but you find both on the net, "cultivable cells" and "developable cells"

HTH

developable or cultivatable

viable might also work, but I'm not 100% sure; here is a dictionary entry that may help you decide (Webster):

viable = 1: capable of living esp. capable of surviving outside the mother's womb without artificial support 2: capable of growing or developing (seeds, eggs) 3a: capable of working, functioning or developing adequately (alternativeisi) 3b: capable of existence and development as an independent unit (the colony is now a viable state) 3c: having a reasonable chance of succeeding

Good luck!

I'm more or less with Vesna, not (yet) convinced by Sven.

Quotation:
In Austrian law, the embryo is not defined and the term "developable
cells" is defined as inseminated ova and cells developed from them

This actually supports the ESC but the E seems over the top to me.

My understanding is that "stem cells" is now the common English term for this.

One could argue (against me) that in connection with a law, one should use terms that refer clearly back to the original language.