  The assumption that the Standard Model is an Effective Field Theory (SM EFT)
of a more fundamental theory at a higher, than electroweak, energy scale,
implies a growth of cross-sections for electroweak Vector Boson Scattering
(VBS) processes signalling the appearance of a resonance (or resonances) nearby
that scale. In this article, we investigate in detail SM EFT effects from
dimension-6 operators in VBS with like-sign-$W$ production in fully leptonic
decay modes at the High Luminosity LHC (HL-LHC). We find that these effects are
important for a handful of operators, most notably for the operator composed of
three $SU(2)$ field strength tensors responsible for strong transversely
polarized vector boson interactions. Current global fits on Wilson-coefficients
allow for a signal immediately permissive at the HL-LHC if not accessible at
the current LHC-dataset.
