arXiv:2611.13437v1 Announce Type: new Abstract: Enforcing export controls on AI accelerators requires verifying where a chip operates after deployment. Round-trip time measurements can bound a chip's distance from a trusted landmark, but any jitter in honest replies forces the verifier to loosen its timeout, giving an attacker slack to relay traffic over fiber from a restricted region. Prior approaches either cross the untrusted host stack or rely on noisy power-line channels that inflate this slack. We present 5G CATS, a location certification system that pairs a co-packaged 5G radio, cryptographic engine, and hardware interlock on the GPU package with 5G Ultra-Reliable Low-Latency Communication (URLLC) base stations. Terminating the radio link inside the package removes the host software, PCIe fabric, and baseboard management controller from the verification path. We map an authenticated challenge-response protocol onto 5G's slot structure, replace permanent key erasure with short-lived execution leases, and specify a cross-check of the chip's reported serving cell against the carrier's own attachment records. In ns-3 and 5G-LENA simulations of an unloaded cell, our URLLC-based radio profile narrows the 99.9th percentile round-trip spread to 2.60 ms, more than ten times narrower than default 5G. A tracer rejects every round of a fiber relay from 300 km, against 2,000 km for default 5G. Against a 3,000 km attacker, a tracer stays safe at up to 1,410 km from the chip, against at most 619 km for PowerCATS's published model, while default 5G is never safe.