  We revisit the issue of conservation of magnetic helicity and the
Woltjer-Taylor relaxation theory in magnetohydrodynamics in the context of weak
solutions. We introduce a relaxed system for the ideal MHD system, which
decouples the effects of hydrodynamic turbulence such as the appearance of a
Reynolds stress term from the magnetic helicity conservation in a manner
consistent with observations in plasma turbulence. As by-products we answer two
open questions in the field: We show the sharpness of the $L^3$ integrability
condition for magnetic helicity conservation and provide turbulent bounded
solutions for MHD dissipating energy and cross helicity but with (arbitrary)
constant magnetic helicity.
