Large Language Models (LLMs) are increasingly being adopted in enterprise environments, where employees may intentionally or accidentally submit prompts containing information that could cause legal or economic harm if leaked. Organizations may define categories of information (policies) that are prohibited from being submitted to commercial LLMs, but these definitions can vary between companies and evolve over time. This variability makes parametric classifiers less practical, as they require retraining whenever policies change. Here, we present Q-CAT, a non-parametric policy enforcement system that classifies user queries based on given categories of information that can change dynamically. The system operates by matching embedded user queries to synthetically generated queries in the database. This design enables low-cost policy updates through simple database modification, without retraining, while maintaining low latency. A comparison with strong prompt-based LLM baselines shows that Q-CAT delivers competitive performance in static environments, while offering practical advantages in dynamic policy settings, where policies change and the Query Pool can be updated from logs. Moreover, Q-CAT is up to two orders of magnitude faster than comparable-performance baselines in our experimental setup.