  We analyze the existing evidence that BL Lacertae objects (BL Lacs) are
sources of the highest-energy cosmic rays. We argue that three independent
signatures observed in the real data -- (1) improvement of correlations with
corrections of trajectories for the Galactic magnetic field; (2) connection
between gamma-ray and UHECR emissions; (3) non-uniform distribution of
correlating rays over the sky -- are consistent with the hypothesis that a
substantial fraction of cosmic rays in the energy range 40-60 EeV are protons
accelerated in BL Lacs.
