We have measured the EPR spectrum of dilute ${\mathrm{Gd}}^{3+}$ ions substituting for ${\mathrm{Eu}}^{3+}$ in ${\mathrm{Eu}}_{2}$${\mathrm{CuO}}_{4}$. Each one of the resonance lines shows a splitting into two or more weaker lines below ${\mathit{T}}_{\mathit{N}}$\ensuremath{\approxeq}215 K. The simultaneous appearance of a low-field microwave-absorption signal is attributed to the onset of long-range antiferromagnetic ordering with a weak ferromagnetic component. The splitting of the EPR spectrum is associated with different Gd sites in the magnetically ordered structure. A reduction of the local symmetry of the rare-earth sites below ${\mathit{T}}_{\mathit{N}}$ is described in terms of an internal magnetic field lying in the ab plane and additional crystal-field terms related to local crystallographic distortions. Dipolar and exchange contributions to the internal field are discussed. Possible random static displacements of the oxygen atoms in the ${\mathrm{CuO}}_{2}$ planes and their role in the development of the weak ferromagnetism and the presence of internal fields at the Gd sites are also analyzed. A strong dependence of the Gd EPR spectrum and the microwave absorption on the magnetic history of the samples has been observed, suggesting the formation of magnetic domains or a glassy state.