where two spin-$1/2$ systems $A$ and $B$ are prepared in such a way that those knowing about the preparation procedure assign an entangled state, for instance, the state $\frac{1}{2} (|+\rangle_A|-\rangle_B-|-\rangle_A|+\rangle_B)$ for their combined spin degrees of freedom. Assume further that the two systems $A$ and $B$ have been brought far apart and an agent Alice, located at the first system $A$, measures its spin in a certain direction. Having registered the result and having applied the projection postulate, she assigns two no longer entangled states to $A$ and $B$, which depend on the choice of observable measured and on the measured result. Another agent, Bob, located at the second system $B$, may also perform a spin measurement (in the same or in a different direction of spin) and proceed to assign a pair of no longer entangled states to the two systems in an analogous way. Now the intriguing challenge concerning the compatibility of quantum theory and relativity theory is to specify at which time which system is in which state and to do so in a Lorentz invariant manner. The difficulty is especially blatant for cases where the measurements carried out by Alice and Bob occur in spacelike separated 