A study is presented of anomalous
H
V
V
interactions of the Higgs boson, including its
C
P
properties. The study uses Higgs boson candidates produced mainly in vector boson fusion and gluon fusion that subsequently decay to a pair of
τ
leptons. The data were recorded by the CMS experiment at the LHC in 2016 at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of
35.9
 
 
fb
−
1
. A matrix element technique is employed for the analysis of anomalous interactions. The results are combined with those from the
H
→
4
ℓ
decay channel presented earlier, yielding the most stringent constraints on anomalous Higgs boson couplings to electroweak vector bosons expressed as effective cross section fractions and phases: the
C
P
-violating parameter
f
a
3
cos
(
ϕ
a
3
)
=
(
0.00
±
0.27
)
×
10
−
3
and the
C
P
-conserving parameters
f
a
2
cos
(
ϕ
a
2
)
=
(
0.0
8
+
1.04
−
0.21
)
×
10
−
3
,
f
Λ
1
cos
(
ϕ
Λ
1
)
=
(
0.0
0
+
0.53
−
0.09
)
×
10
−
3
, and
f
Z
γ
Λ
1
cos
(
ϕ
Z
γ
Λ
1
)
=
(
0.
0
+
1.1
−
1.3
)
×
10
−
3
. The current dataset does not allow for precise constraints on
C
P
properties in the gluon fusion process. The results are consistent with standard model expectations.