The nanopatterning of surfaces and thin films with pattern dimensions of less than 100 nm is challenging for laser processing in particular in the case of large-area, low-cost fabrication. Self-assembly processes, however, provide a mechanism of pattern generation in this dimensional range offering an alternative fabrication method. The current work focuses on high-temperature, short-time laser annealing of PS-b-PMMA block copolymer (PS-b-PMMA BCP: poly(styrene-block-methyl methacrylate)) films on fused silica samples to achieve self-assembly into vertical lamellas with periods of approximately 50 nm. BCP samples were irradiated with a focussed CO2-laser beam for studying the influence of the laser power P-L and the scanning speed vs on the lamellae formation in BCP films. The formation of lamellae is observed in the centre of the laser track at sufficient laser irradiation (PL: 2 to 15 W, vs: 1 to 250 mms(-1)). With increasing laser irradiation, first the quality of the lamellas improves to a certain point but thereafter a partial degradation of the BCP and dewetting of the BCP film occurs. The partial degradation of the PMMA micro-phase of the ordered BCP results in a local self-developing process reducing the processing steps for nanopattern formation. The experimental results on laser-induced local self-assembly with irradiation times below 0.1 s are discussed in relation to laser-induced temperature field simulations. Combining self-assembly capabilities of BCP with local heating by laser beams can provide a tool for direct writing of hierarchical nano-/microscale patterns that is useful for various applications mimicking bio-inspired structures.