  The upper bounds from the ATLAS and CMS experiments on the decay rate of the
Higgs boson to two muons provide the strongest constraint on an imaginary part
of the muon Yukawa coupling. This bound is more than an order of magnitude
stronger than bounds from $\mathcal{CP}$-violating observables, specifically
the electric dipole moment of the electron. It excludes a scenario $-$ which
had been viable prior to these measurements $-$ that a complex muon Yukawa
coupling is the dominant source of the baryon asymmetry. Even with this bound,
the muon source can still contribute ${\cal O}(16\%)$ of the asymmetry.
