  We examine dimension-six extensions of the standard electroweak Lagrangian
which are invariant under local \suu -transformations. The dimension-four
trilinear and quadrilinear effective interactions of the vector bosons with one
another are found to coincide with the vector boson interactions previously
derived from global SU(2) weak isospin symmetry broken by electromagnetism.
Supplementing the model by a well-known dimension-six single-parameter
quadrupole interaction leads to the most general vector boson self-couplings
that can be obtained by addition of dimension-six terms to the standard
Lagrangian. We examine in some detail another SU(2)xU(1)-symmetric interaction
which contains W_3-B mixing and modifies both vector boson self-couplings and
fermionic interactions. Independently of being strongly constrained by the LEP
1 data, the addition of this interaction to the above-mentioned non-standard
ones does not change the form of the trilinear and quadrilinear non-standard
self-couplings of the vector bosons. Therefore, while being interesting in
itself with respect to LEP~1 physics, this term is irrelevant with respect to
the phenomenology of the vector-boson self-interactions.
