III-Nitride vertical-cavity surface-emitting lasers (VCSELs) have attracted much attention during the last two decades. Control of the laser polarization in VCSELs is one of the main challenges that needs to be addressed for real applications. In this work a novel polarization locking technique for GaN VCSELs is presented by employing birefringent nanoporous distributed Bragg reflectors (DBRs). The birefringence arises from a nanophotonic effect of evanescent field enhancement in the anisotropically aligned nanopores. Furthermore, the birefringence dependence over the nanopores morphology is explored. A fully electrically injected blue VCSEL with polarization locking is demonstrated. As presented, this technique allows to individually define the polarization angle in a planar array, opening the path to novel applications.