We find that an isolated canonical neutron star (1012Gdipole, 10 s rotational period) can accrete at most 106g/s from the interstellar medium regardless of its ambient density. Solitary neutron stars are therefore so fuel starved (even if placed in dense molecular clouds) that the thermonuclear model cannot account for the majority of gamma‐ray bursts. The derived upper limit on accretion rate is a consequence of the propeller mechanism and of the ionizing power of accretion‐caused radiation. Implications of this upper limit for the cyclotron‐line interpretation of GB 870303 are discussed. We also show that gamma‐ray bursts as a class cannot be powered by large crustal superfluid glitches of neutron stars produced at current birthrates. If gamma‐ray bursts are powered by internal sources of energy of neutron stars, such as rotational or nuclear free energy, typical rotation periods cannot fall in the range 10 s to 500 s.